"Plug In Baby" is an electronic rock song written in the key of B minor. It's mainly guitar and bass-driven, and moves at a tempo of 135 bpm. The guitar riff is based on the harmonic minor scale. The song was first recorded as a demo in 1997, although it featured a different guitar riff. The beginning of the riff shows similarities to the toccata from Bach's "Toccata and Fugue in D minor, BWV 565". Total Guitar voted the riff as the 13th best of all-time in 2004. In 2011, Spinner.com named "Plug In Baby" the 46th greatest guitar riff of all time, citing its "play on Bach's 'Toccata and Fugue in D minor, BWV 565'."
The 1997 studio demo of the song lacked the main riff of the song, although there were numerous similarities in the lyrics and structure. "Plug In Baby" was to be re-recorded under the wishes of Maverick to coincide with the US tour promoting the Origin of Symmetry album. As Maverick wished Matt to tone down the falsetto on the song, Muse left the label and "Plug In Baby", as well as the rest of the album, remained unreleased in the US until 2005.
The music video depicts the band in a room playing their instruments, with cut-aways to scenes of women, which step by step are revealed to be at least part bionic with tendrils hanging down. These connect to the title 'plug in baby' connecting the women to be electronic 'creations', or a sort of self-assembly beings. The video also has some scenes with electronic equipment affecting women who use them, one being a hairdryer and the other a set of ear phones, both leading to visual indications that they are somehow under control or possibly even being possessed. The end shows the lead singer of the band Matt Bellamy paused in a stress pose, in a way that looks like he has 'powered down' at the end of the song, again linking to the idea of bionic beings that the video has played with the whole way through.