"Battery" is a song by the American heavy metal band Metallica. It is the opening track and was released as the second single from their third album, Master of Puppets. As with the opening track from Ride the Lightning (titled "Fight Fire With Fire"), Battery begins with a slow, clean guitar part. In this case, four acoustic guitars are layered harmonically before the drums and bass come in with distorted guitars playing a more melodic version of the acoustic part. This lasts until 1:06, when the guitars cut into a very fast minimalist thrash metal riff that is the basis for the rest of the song, the song also features a heavy bass line by Cliff Burton and a wild and difficult drum beat by Lars Ulrich. In live concerts, the beginning is not played by the band but instead the actual recording is used (recently dropped 1/2 step in key, since the band tunes 1/2 step down).

In keeping with the general "control" theme of Master of Puppets, the lyrics of "Battery" discuss the control that anger can have over one's behavior. The title refers to "battery" in the sense of "assault and battery", as shown by these lyrics: "Smashing through the boundaries / Lunacy has found me / Cannot stop the battery". In addition to the thematic interpretation of "battery" as control, the song is an homage to the Old Waldorf Club on Battery Street, San Francisco.^{[citation needed]}

"Battery" used to be a constant part of the band's live set list, frequently as the opening or closing song. In some cases, it is also used as a song before the intermission. Since 2008 the song has usually been dropped from setlists. When played, the song may stop before the interlude, and James Hetfield asks the crowd "Are you alive?... How does it feel to be alive?" (this can be heard on the live album S&M) and followed by the solo played by Kirk Hammett.

As seen in the documentary Some Kind of Monster, the auditioning of future bassist Robert Trujillo started, on his request, with "Battery".

In the live version of the song played on the Live Shit: Binge & Purge album, intros to the songs "No Remorse", "Ride the Lightning", and "So What?" are played in the song. When performed with the San Francisco Symphony in 1999, the intro up to the thrash riff was instead played by string players in the symphony, utilizing pizzicato in the beginning (the original acoustic) then with bows for the rest.

Allmusic's Steve Huey called the songs "Battery" and "Damage, Inc.", "two slices of thrash mayhem".^[1]

• This song (along with the entire Master of Puppets album) was covered by Dream Theater as part of their world tour in 2002 and has been released as an official Bootleg recording.
• This song was covered by the band Machine Head for Kerrang!'s Master of Puppets: Remastered, and is also included as a bonus track on some versions of their album The Blackening.
• The song was also covered by the a cappella metal band Van Canto on their debut album "A Storm to Come".
• On "Animetal Rebirth Heroes", Animetal uses the riff for "Battery" throughout the entire song "Touch" with some changes in between.
• This song was covered by the band Ensiferum for Evil Ultimate Metal Covers No. 55. It was also featured on the single "Tale of Revenge".
• Beatallica a mash-up band that combines Metallica and The Beatles combined Battery with The Ballad of John and Yoko to create The Battery Of Jaymz And Yoko on their Masterful Mystery Tour
• Die Krupps covered the song for A Tribute to the Four Horsemen.
• This song was covered by Eric AK (Flotsam & Jetsam), Dave Lombardo, Mike Clark, and Robert Trujillo for Metallic Assault: A Tribute to Metallica. Dave Lombardo would play the song with Metallica on stage when Lars Ulrich missed the 2004 Download Festival, and Robert Trujillo would become a member of Metallica in 2003.
• This song was covered by Prototype for Phantom Lords - A Tribute to Metallica released by Dwell Records in 2002.
• Harp tribute duo Harptallica covered the song's introduction on their album Harptallica: A Tribute.
• "Battery" is a playable song in Rock Band 2, among one of the hardest to perform for all instruments.
• It is also a featured track in the band's videogame, Guitar Hero: Metallica as one of the Expert Plus songs for the drums.
• Pop-punk band Lagwagon borrows the line "smashing through the boundaries/lunacy has found me" for their song "Raise A Family" found on their 2000 release "Let's Talk About Leftovers."
• The Deftones covered the song on the second night of the band's 'One Love For Chi' concerts in 2009 with accompaniment from Dave Lombardo of Slayer on drums, Alexi Laiho of Children of Bodom on guitar, Rob Trujillo of Metallica on bass, Daron Malakian and Shavo Odadjian of System of a Down on guitar and bass respectively, and Greg Puciato of The Dillinger Escape Plan on vocals.^{[citation needed]}