"One" was written in November 1987 by Metallica's principal composers James Hetfield and Lars Ulrich. The song was released in 1989 as the third and final single from the album. For the first 17 seconds of the song there are a series of sound effects with a battle theme, an artillery barrage and helicopter are heard and continues slightly over a clean tone guitar intro by Hetfield before Kirk Hammett comes in over the top with a clean-toned solo. The song speeds up after Ulrich's drums come in and continues until each chorus, when the guitars become heavy and distorted before returning to clean. There is a second solo by Hammett halfway through the song, before lyrics cut out and the song gradually gets more heavy and distorted until the "machine gun" guitar build up (played alongside double bass drums) before the next, often highly praised, guitar solo by Hammett, and a final dual solo by Hammett and Hetfield. The song begins in 4/4 time, and later 3/4 as well as 2/4.
In 1991, James Hetfield told Guitar World that he wrote the song's opening B-G chord change (he miscalls it a 'modulation') based on an idea prompted by the Venom song "Buried Alive" from their second studio album, Black Metal.
I had been fiddling around with that B-G modulation for a long time. The idea for the opening came from a Venom song called "Buried Alive". The kick drum machine-gun part near the end wasn't written with the war lyrics in mind, it just came out that way. We started that album with Mike Clink as producer. He didn't work out so well, so we got Flemming to come over and save our asses.
The song's theme and lyrics are based on Dalton Trumbo's 1939 novel Johnny Got His Gun, telling the tale of a soldier who is hit by an artillery shell and loses his limbs, eyes, ears and mouth. His mind functions perfectly, however, leaving him trapped inside his own body (which could also be described as a special form of locked-in syndrome). Trumbo directed the movie adaptation in 1971, from which the footage for the "One" music video is taken.
"One" is a favorite of many Metallica fans, and thus is a fixture of the band's live performances. When played live, the song is usually played with guitars tuned down by one semitone (a permanent fixture of their studio and live work since the post Metallica era, save for Death Magnetic in the case of the former) and is preceded by pyrotechnics and the same sounds of war such as machine guns, and bombs exploding as heard on the recorded version. The song also features heavy strobe lighting during the heavier half of the song, namely before the Hammett solo. The song was also featured on S&M, Metallica's album of live performances in collaboration with the San Francisco Symphony Orchestra, conducted by Michael Kamen. Another mentionable performance was at the Grammy Awards 2014, having pianist Lang Lang accompanying the band on an acoustic grand piano.
Three versions of the "One" music video were made; the first (the longest, album version) contained scenes of both the band and scenes from the movie. The second was simply a shortened version of the first and the third, often known as the "jammin' version", lacked scenes from the movie (the song and video fades at the last bridge in the third version).
Like many other music videos from Metallica, "One" puts great emphasis on the performances of the band members as musicians, with many shots of Hetfield, Newsted and Hammett's hands picking and fretting. The video features the band members in a typical early Metallica fashion: playing (as if in rehearsal) in some sort of warehouse, in tight formation around Ulrich's drum kit, and dressed in casual street clothes and with long untamed hair.
In the music video, it can be clearly seen that both Hetfield and Hammett are playing ESP guitars; Jason Newsted is on a 5-string Wal bass. It is also clear that Newsted is playing bass with his fingers at the start of the song, but later switches to a pick.
Two of the three versions of the "One" music video appear on 2 of One, a VHS released on July 1, 1990 and both would again be featured on the band's 2006 music video compilation DVD.
The music video was ranked 38 on Rock on the Net: MTV: 100 Greatest Music Videos and number 1 on Fuse's No. 1 Countdown: Rock and Roll Hall of Fame Special Edition.
"One" was covered by the band Korn as part of the MTV Icon Metallica tribute TV show. This cover version is featured as a hidden track on their 2003 album Take a Look in the Mirror and their album Live and Rare. However, Korn's version was shortened to a little more than four minutes, like most performances at MTV Icons, and lacks much of the second half of the song, including the final guitar solo. The bridge is also played often at live shows as an outro to their song "Shoots and Ladders"; however, as of 2009, "Fake" usually ends with the "One" outro.
"One" is featured in the video game Guitar Hero III: Legends of Rock, where it is mostly remembered as one of the most difficult songs to appear in the series, mostly due to the fast-paced solos that comprise the second half of the song. The song appeared once again in Guitar Hero: Metallica, with its difficulty toned down.
In 2008, Shout! Factory released a film adaptation of the stage play Johnny Got His Gun; the DVD release included the music video for "One" and the original film.
"One" is the walkup music for Oakland Athletics closer Grant Balfour. When Balfour enters the game to this song, raucous Oakland fans will wildly punch the air and headbang; this is known as "Balfour Rage".