The song was performed with orchestral accompaniment on the album S&M. It was the band's first number one song on the US BillboardHot Mainstream Rock Tracks chart, as well as their first and only song to hit the top 10 of the Billboard Hot 100, peaking at number 10.
An early demo version of this song was entitled "F.O.B.D" (recorded on December 8, 1995), because it reminded the band members of the Soundgarden song "Fell on Black Days," in that the "It grips you...It stains you..." refrain is in the same 6/4 time signature that "Fell on Black Days" is in. The band can be heard saying "Fell on Black Days" on the fanclub-only Fancan 1 CD just prior to jamming on a portion of "Until It Sleeps." The 10" vinyl version of the single is red in color.
The lyrics of the song, written by Hetfield, address his mother's battle with cancer, to which Hetfield's "it" refers. They can be seen as either describing the emotional pain he feels for the loss, or the physical pain his mother was feeling while she was ill. Both of his parents were Christian Scientists, and did not believe in medicine. The lyrics are also interpreted as dealing with anger issues. Hetfield's father, Virgil, died in late 1996, during Metallica's Load tour.