Background and recording
Metallica's 1983 debut Kill 'Em All laid the foundation for thrash metal with its aggressive musicianship and vitriolic lyrics. The album revitalized the American underground scene, and inspired similar records by contemporaries. The band's second album Ride the Lightning extended the limits of the genre with its more sophisticated songwriting and improved production. The album caught the attention of Elektra Records representative Michael Alago, who signed the group to an eight-album deal in the fall of 1984, halfway through the album's promotional tour. Elektra reissued Ride the Lightning on November 19, and the band began touring larger venues and festivals throughout 1985. After parting with manager Jon Zazula, Metallica hired Q Prime executives Cliff Burnstein and Peter Mensch. During the summer, the band played the Monsters of Rock festival at Castle Donington, alongside Bon Jovi and Ratt to an audience of 70,000.
Metallica was motivated to make an album that would impress critics and fans, and began writing new material in mid-1985. Lead vocalist and rhythm guitarist James Hetfield and drummer Lars Ulrich were the main songwriters on the album, already titled Master of Puppets. The two developed ideas at a garage in El Cerrito, California, before inviting bassist Cliff Burton and guitarist Kirk Hammett for rehearsals. Hetfield and Ulrich described the songwriting process as starting with "guitar riffs, assembled and reassembled until they start to sound like a song". After that, the band came up with a song title and topic, and Hetfield wrote lyrics to match the title. Master of Puppets is Metallica's first album not to feature songwriting contributions from former lead guitarist Dave Mustaine. Mustaine claimed he had co-written "Leper Messiah", based on an old song called "The Hills Ran Red". The band denied this, but stated that one section incorporated Mustaine's ideas.
When I saw two kids who worked there in London wearing T-shirts of a local San Francisco band, I knew I was onto something. When I heard their record, I knew they were the one band that could sell to both mainstream and underground metal audiences.
— Cliff Burnstein, on signing Metallica
The band was not satisfied with the acoustics of the American studios they considered, and decided to record in Ulrich's native Denmark. Ulrich took drum lessons, and Hammett worked with Joe Satriani to learn how to record more efficiently. Ulrich was in talks with Rush's bassist and vocalist Geddy Lee to produce the album, but the collaboration never materialized because of uncoordinated schedules. Metallica recorded the album with producer Flemming Rasmussen at Sweet Silence Studios in Copenhagen, Denmark, from September 1 to December 27, 1985. The writing of all the songs except "Orion" and "The Thing That Should Not Be" was completed before the band's arrival in Copenhagen. Rasmussen stated that the band brought well-prepared demos of the songs, and only slight changes were made to the compositions in the studio. The recording took longer than the previous album because Metallica had developed a sense of perfectionism and had higher ambitions. Metallica eschewed the slick production and synthesizers of contemporary hard rock and heavy metal albums by Bon Jovi, Iron Maiden, and Judas Priest. With a reputation for drinking, the band stayed sober on recording days. Hammett recalled that the group was "just making another album" at the time and "had no idea that the record would have such a range of influence that it went on to have". He also said that the group was "definitely peaking" at the time and that the album had "the sound of a band really gelling, really learning how to work well together".
Rasmussen and Metallica did not manage to complete the mixtapes as planned. Instead, the multitrack recordings were sent in January 1986 to Michael Wagener, who finished the album's mixing. The cover was designed by Metallica and Peter Mensch and painted by Don Brautigam. It depicts a cemetery field of white crosses tethered to strings, manipulated by a pair of hands in a blood-red sky. Ulrich explained that the artwork summarized the lyrical content of the album—people being subconsciously manipulated. The original artwork was sold at Rockefeller Plaza, New York City for $28,000 in 2008. The band mocked the warning stickers promoted by the PMRC with a facetious Parental Advisory label on the cover: "The only track you probably won't want to play is 'Damage, Inc.' due to the multiple use of the infamous 'F' word. Otherwise, there aren't any 'shits', 'fucks', 'pisses', 'cunts', 'motherfuckers', or 'cocksuckers' anywhere on this record".
The album was recorded with the following equipment: Hammett's guitars were a 1974 Gibson Flying V, a Jackson Randy Rhoads, and a Fernandes Stratocaster copy; Hetfield used a Jackson King V played through a Mesa Boogie Mark IIC+ amplifier modified as a pre-amp; Burton played an Aria Pro II SB1000 through Mesa Boogie amplifier heads and cabinets; Ulrich played Tama drum equipment, and borrowed a rare S.L.P. Black Brass from Def Leppard drummer Rick Allen.