Metallica is an American heavy metal band from Los Angeles, California. The band's fast tempos, instrumentals, and aggressive musicianship placed them as one of the founding "big four" of thrash metal alongside Slayer, Megadeth, and Anthrax. Metallica was formed in 1981 when James Hetfield responded to an advertisement that drummer Lars Ulrich had posted in a local newspaper. The current line-up features founders Hetfield and Ulrich, longtime lead guitarist Kirk Hammett and bassist Robert Trujillo, who joined the band in 2003. Previous members of the band are lead guitarist Dave Mustaine, who went on to found Megadeth, bassists Ron McGovney, Cliff Burton, and Jason Newsted. The band also had a long collaboration with producer Bob Rock, who produced all of its albums from 1990 to 2003 and served as a temporary bassist between the departure of Newsted and the hiring of Trujillo.
The band earned a growing fan-base in the underground music community and critical acclaim with its first four albums, with their third, Master of Puppets, described as one of the most influential and heavy thrash metal albums.