Metallica /məˈtælɨkə/ 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 formed in 1981 when James Hetfield responded to an advertisement that drummer Lars Ulrich had posted in a local newspaper. As of 2003, the line-up features long-time lead guitarist Kirk Hammett (who joined the band in 1983) and bassist Robert Trujillo (a member since 2003) alongside Hetfield and Ulrich. Previous members of the band are lead guitarist Dave Mustaine (who went on to found the band Megadeth), and 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 (1986), described as one of the most influential and "heavy" thrash metal albums. Metallica achieved substantial commercial success with their eponymous fifth album (also known as The Black Album), which debuted at number one on the Billboard 200. With this release the band expanded its musical direction resulting in an album that appealed to a more mainstream audience.