|Stylistic origins||Doom metal, hardcore punk, Southern rock, grunge|
|Cultural origins||Mid 1980s, United States|
|Typical instruments||Electric guitar, bass, drums, vocals, keyboards|
|Southern United States|
Sludge metal (sometimes referred to simply as "sludge") is an extreme genre of music that melds elements of doom metal and hardcore punk, and sometimes Southern rock. Sludge metal is typically harsh and abrasive, often featuring shouted or screamed vocals, heavily distorted instruments and sharply contrasting tempos. While the style was anticipated by the Melvins from Washington, many of its earliest pioneers were from the city of New Orleans.
Sludge metal generally combines the slow tempos, heavy rhythms and dark, pessimistic atmosphere of doom metal with the aggression, shouted vocals and occasional fast tempos of hardcore punk. As The New York Times put it, "The shorthand term for the kind of rock descending from early Black Sabbath and late Black Flag is sludge, because it's so slow and dense." Many sludge bands compose slow-paced songs that contain brief hardcore passages (for example, Eyehategod's "Depress" and "My Name Is God"). Mike Williams, a founder of the sludge style and member of Eyehategod, suggests that "the moniker of sludge apparently has to do with the slowness, the dirtiness, the filth and general feel of decadence the tunes convey". However, some bands emphasize fast tempos throughout their music. The string instruments (electric guitar and bass guitar) are downtuned and heavily distorted and are often played with large amounts of feedback to produce a thick yet abrasive sound. Additionally, guitar solos are often absent. Drumming is often performed in typical doom metal fashion. Drummers may employ hardcore D-beat or double-kick drumming during faster passages, or through the thick breakdowns (which are characteristic of the sludge sound). Vocals are usually shouted or screamed, and lyrics are generally pessimistic in nature. Suffering, drug abuse, politics and anger towards society are common lyrical themes.
Many sludge metal bands from the Southern United States incorporate Southern rock influences, although not all sludge bands share this style. There is some controversy as to whether the term refers to only the style emerging from New Orleans and later the American South more broadly, or to "a complete consciousness in the heads of like-minded Black Flag/Black Sabbath influenced scenes and individuals all over the world". So-called "atmospheric" sludge bands adopt a more experimental approach and compose music with an ambient atmosphere, reduced aggression and philosophical lyrics. Due to the similarities between sludge and stoner metal, there is often a crossover between the two genres, but sludge metal generally avoids stoner metal's usage of psychedelia. Sludge metal also bears some musical and lyrical resemblance to crust punk, due to the usage of political lyrics and thick, "dirty" guitar sounds.
Along with Black Flag and Black Sabbath, musicians cited by pioneers of the style as influential include Mississippi John Hurt, Lynyrd Skynyrd, Greg Ginn, Trouble, Carnivore, Saint Vitus, Gore, Righteous Pigs, Amebix and Swans. Early sludge metal groups also borrowed from the industrial music of SPK, Throbbing Gristle, Chrome and Swans. The beginnings of sludge have been traced to the "slow punk" of Flipper, Swans' 1984 album Cop, and Black Flag's album My War.
Perhaps the most significant influence was Melvins, a band from the state of Washington. Their earliest releases, Six Songs (1986) and Gluey Porch Treatments (1987), are often regarded as the first sludge records. At this time, the band was also an important member of the Washington grunge scene. Another prominent band from the Washington grunge scene, Alice in Chains have also been influential to early sludge metal with their second album Dirt. Neurosis, from Oakland, were also significant early practitioners.
At the beginning of the 1990s, a number of bands from Louisiana (particularly New Orleans with its metal scene) took these influences and developed the style that would be known as sludge. Eyehategod (formed in 1988), Crowbar (formed in 1989 as The Slugs) and Acid Bath (formed in 1991) pioneered this movement. On the East Coast, Buzzov*en (formed in 1989), 16 (formed in 1990) and Grief (formed in 1991) adopted a slower-paced approach to the emerging genre.
According to Phil Anselmo,
Back in those days, everything in the underground was fast, fast, fast. It was the rule of the day. But when the Melvins came out with their first record, Gluey Porch Treatments, it really broke the mold, especially in New Orleans. People began to appreciate playing slower. With that, all the old Black Sabbath came back around and then you start digging and you come to your Saint Vitus, your Witchfinder General, your Pentagram, etc.— 
Sludge metal subsequently spread throughout the Southern and Eastern United States.
Jose Carlos Santos notes a focus shift as a result of the impact of the British group Iron Monkey's first album in 1997:
Coincidence or not, it seemed like the sludge floodgates opened to the rest of the world, and in the past decade small pockets, or mini-scenes, can be spotted in just about any country you'd care to mention.— 
These include the Japanese group Corrupted and contemporary American groups such as Dumb Numbers, Lair of the Minotaur, Old Man Gloom and Kylesa. In addition, the U.S. state of Georgia has been identified as major sources of new sludge groups such as Mastodon, Baroness, Black Tusk, and Kylesa.
During the late 1990s, many sludge metal bands began to incorporate post-rock elements into their music. This post-rock/sludge crossover was greatly inspired by the experimental style of Neurosis during the early to mid 1990s, and is performed by prominent bands such as Isis, Cult of Luna and Pelican.
These bands are the pioneers of the genre or are strongly influenced by those bands. Many are from the Southern United States, excluding the Melvins who are from Montesano, Washington and Iron Monkey who are from England.
- Acid Bath
- Corrosion of Conformity
- Harvey Milk
- Iron Monkey
- Superjoint Ritual
These bands have mixed typical stoner metal traits with typical sludge metal traits, and may be considered a part of both genres.
- Electric Wizard
- High on Fire
- Mico de Noche
Other fusions with sludge metal
- Alice in Chains (sludge metal, grunge and alternative metal
- Baroness (sludge metal and progressive metal)
- Black Label Society (sludge metal, hard rock and Southern rock)
- Black Tusk (sludge metal, hardcore punk and stoner rock)
- Boris (sludge metal and drone metal)
- Cancer Bats (sludge metal, hardcore punk and southern rock)
- Dumb Numbers (sludge, doom, noise rock, "swooning feedback pop")
- Every Time I Die (sludge metal, mathcore, metalcore)
- Dystopia (sludge metal and crust punk)
- Fudge Tunnel (sludge metal, noise rock and alternative metal)
- Helms Alee (sludge metal and shoegaze)
- Isis (sludge metal and post-rock)
- KEN Mode (sludge metal, noise rock and post-hardcore)
- Kingdom of Sorrow (sludge metal and metalcore)
- Lair of the Minotaur (sludge metal and thrash metal)
- Mastodon (sludge metal, progressive metal and alternative metal)
- Mistress (sludge metal and death metal)
- Part Chimp (sludge metal and noise rock)
- Red Fang (sludge metal and stoner rock)
- Soilent Green (sludge metal and grindcore)
- The Ocean (sludge metal, progressive metal and post-metal)
- Will Haven (sludge metal and metalcore)
- Whores (sludge metal and noise rock)
- "AllMusic: Doom Metal". AllMusic. Retrieved 2012-11-19.
- Huey, Steve. "Eyehategod". AllMusic. Retrieved 2008-09-12.
- "Pop/Jazz Listings, page 2". The New York Times. 2007-10-05. Retrieved 2008-07-12.
- York, William. "Eyehategod - In the Name of Suffering". AllMusic. Retrieved 2008-09-12.
- "Sludge Special", p. 43.
- York, William. "Eyehategod - Dopesick". AllMusic. Retrieved 2008-09-12.
- York, William. "Eyehategod - Take as Needed for Pain". AllMusic. Retrieved 2008-09-12.
- York, William. "Soilent Green - Sewn Mouth Secrets". AllMusic. Retrieved 2010-05-24.
- Jeffries, Vincent. "Crowbar - Crowbar". AllMusic. Retrieved 2008-09-12.
- Kennedy, Patrick. "Buzzov-en - To a Frown". AllMusic. Retrieved 2008-09-12.
- Kennedy, Patrick. "Buzzov-en - Sore". AllMusic. Retrieved 2008-09-12.
- York, William. "Acid Bath - When the Kite String Pops". AllMusic. Retrieved 2008-09-12.
- Huey, Steve. "Corrosion of Conformity". AllMusic. Retrieved 2008-09-02.
- York, William. "Soilent Green". AllMusic. Retrieved 2008-09-02.
- Downey, Ryan J. "Isis". AllMusic. Retrieved 2008-09-02.
- Serba, John. "Bongzilla - Gateway". AllMusic. Retrieved 2008-09-02.
…sounding like a cross between Sleep's drowsy, Black Sabbathy meanderings and Electric Wizard/Burning Witch-style gut-curdling, muddy sludge.
- Mason, Stewart. "Kylesa". AllMusic. Retrieved 2008-09-02.
…elements of hardcore punk, psychedelic stoner rock, technical speed metal, and good old-fashioned Black Sabbath sludge appear in their music.
- "Sludge Special", p. 44.
- Conway, James. "How Haven't You Heard… Alice in Chains – Dirt". Vulture Hound Magazine. Retrieved 2012-11-16.
- Christopher, Michael. "Alice in Chains: Dirt". PopMatters. Retrieved 2012-11-16.
- "Sludge Special", p. 51.
- Huey, Steve. "Crowbar". AllMusic. Retrieved 2008-09-02.
- York, William. "Acid Bath". AllMusic. Retrieved 2008-09-02.
- York, William. "Buzzov-en". AllMusic. Retrieved 2008-09-02.
- J. Bennett, "Hazardous Prescription", Precious Metal: Decibel Presents the Stories Behind 25 Extreme Metal Masterpieces, Albert Mudrian, ed., Da Capo Press, p. 177.
- J. Bennett, "Pillar of Eternity", Precious Metal: Decibel Presents the Stories Behind 25 Extreme Metal Masterpieces, Albert Mudrian, ed., Da Capo Press, p. 268.
- "Sludge Special Part 2", p. 41.
- Burgess, Aaron (2006-05-23). "The loveliest album to crush our skull in months". Alternative Press. Retrieved 2008-09-02.
- "Top 10 New Orleans Metal Bands". Yahoo! Voices. 2010-02-18.
- York, William. "Harvey Milk". AllMusic. Retrieved 2014-08-30.
- Kott, Paul. "Iron Monkey". AllMusic. Retrieved 2008-05-19.
- Raggett, Ned. "Melvins - Gluey Porch Treatments". AllMusic. Retrieved 2008-05-19.
- Rivadavia, Eduardo. "Bongzilla". AllMusic. Retrieved 2008-05-19.
- Rivadavia, Eduardo and Koets, Tara. "Electric Wizard". AllMusic. Retrieved 2008-09-02.
…it so effortlessly bridged the stylistic gaps between doom, sludge, stoner, horror, and, at times, even space metal…
- Violante, Isaiah. "High on Fire - Surrounded by Thieves". Pitchfork Media. Retrieved 2008-09-01.
…manufacturing that sludgy, choleric sound…
- "MusicMight :: Artists :: High on Fire". MusicMight. Retrieved 2012-11-21.
- Pegoraro, John (2009-10-13). "Mico de Noche/Brothers of the Sonic Cloth - Split". Stonerrock.com. Retrieved 2010-07-15.
- Levin, Hannah (2009-12-30). "Our Favorite Local Releases of 2009". Seattle Weekly. Retrieved 2010-07-15.
Mico de Noche's two brutal blasts of galvanized sludge are perfectly concise counterpoints.
- Heaney, Greg. "Torche". AllMusic. Retrieved 2008-06-10.
- Rivadavia, Eduardo. "Weedeater". AllMusic. Retrieved 2008-05-19.
- "The Metal's Gone, but the Tunes and Moods Remain". Press-Telegram (Long Beach, CA). Retrieved 2012-09-28.
- Considine, J.D. (1992-10-23). "Alice in Chains breaks free of a style". The Baltimore Sun (Baltimore). Retrieved 2012-09-26.
- Christopher, Michael (September 23, 2003). "Alice in Chains: Dirt". PopMatters. Retrieved 2012-09-28.
- Familton, Chris. "ALICE IN CHAINS The Devil Put Dinosaurs Here". The Music.com.au. Retrieved 2013-05-24.
- Coffey, Russ. "CD: Alice in Chains - The Devil put Dinosaurs Here". The Arts Desk. Retrieved 2013-05-27.
- Deming, Mark. "Baroness". AllMusic. Retrieved 2008-05-21.
- Prato, Greg. "Baroness - Red Album". AllMusic. Retrieved 2008-05-21.
- "MusicMight :: Artists :: Black Label Society". MusicMight. Retrieved 2012-09-28.
- Heaney, Gregory. "Black Tusk biography". AllMusic. Retrieved 2012-02-29.
- Currin, Grayson (2010-07-07). "Taste the Sin review". Pitchfork Media. Retrieved 2012-02-29.
- York, William. "Boris". AllMusic. Retrieved 2012-02-17.
- Colgan, Chris (2010-03-05). "Cancer Bats: Bears, Mayors, Scraps & Bones". PopMatters. Retrieved 2012-02-17.
- Patashnik, Ben. "Cancer Bats Review on BBC". BBC Music. Retrieved 2012-02-17.
- "The Agency Group | Cancer Bats". The Agency Group. Retrieved 2012-02-29.
- Weingarten, Chris (August 5, 2013). "Stream Dumb Numbers' Swooning Feedback-Pop Self-Titled Debut Album". SPIN. Retrieved 17 November 2013.
- Pearis, Bill. "Dumb Numbers released guest-filled LP (Lou Barlow, David Yow, Dale Crover & more), opening for MBV (dates, streams)". Brooklyn Vegan. Retrieved 17 November 2013.
- Rivadavia, Eduardo. "Fudge Tunnel". AllMusic. Retrieved 2012-02-17.
- Heaney, Gregory. "Helms Alee – Overview". AllMusic. Rovi Corporation. Retrieved 2012-11-22.
- AltPress Staff (2011). "File Under: Arty psych-sludge". Alternative Press. Retrieved 2012-11-22.
- Freeman, Phil. "Venerable – Overview". AllMusic. Rovi Corporation. Retrieved 2012-11-22.
- Kasparian, Ryan (2012-03-24). "KEN Mode – Venerable". Profound Lore Records. Retrieved 2012-11-22.
- Prato, Greg. "Kingdom of Sorrow - Kingdom of Sorrow". AllMusic. Retrieved 2012-02-29.
- "Lair of the Minotaur". Sputnikmusic. Retrieved 2009-07-18.
- York, William. "Mastodon". AllMusic. Retrieved 2008-05-19.
- Rivadavia, Eduardo. "Mistress - II: The Chronovisor". AllMusic. Retrieved 2012-02-29.
- "Part Chimp". Rock Action Records (Glasgow). Retrieved 2012-11-22.
- "Soilent Green". Metal Blade Records. Retrieved 2010-05-24.
- Prato, Greg. "Will Haven". AllMusic. Retrieved 2012-02-29.
- Fisher, Greg (October 28, 2013). "Whores. - Clean (staff review)". Sputnikmusic. Retrieved April 8, 2014.
- "Sludge Special". Terrorizer (187): pp. 43–56. August 2009. ISSN 1350-6978.
- "Sludge Special Part 2". Terrorizer (188): pp. 40–57. September 2009. ISSN 1350-6978.