Metallica is an American heavy metal band. The band was formed in 1981 in Los Angeles, California by drummer Lars Ulrich and vocalist/guitarist James Hetfield, and has been based in San Francisco, California for most of its career. The group's fast tempos, instrumentals and aggressive musicianship made them one of the founding "big four" bands of thrash metal, alongside Megadeth, Anthrax and Slayer. Metallica's current lineup comprises founding members Hetfield and Ulrich, longtime lead guitarist Kirk Hammett and bassist Robert Trujillo. Guitarist Dave Mustaine (who went on to form Megadeth) and bassists Ron McGovney, Cliff Burton and Jason Newsted are former members of the band.