An American heavy metal band that was formed in 1981 in Los Angeles by vocalist/guitarist James Hetfield and drummer Lars Ulrich, and has been based in San Francisco for most of its career. The fast tempos, instrumentals and aggressive musicianship made them one of the founding "big four" bands of heavy metal. Metallica's current group members and primary songwriters Hetfield and Ulrich, longtime lead guitarist Kirk Hammett and bassist Robert Trujillo. Metallica earned a growing fan base in the underground music community and won critical acclaim with its first five albums. The band's third album, Master of Puppets (1986), was described as one of the heaviest and most influential thrash metal albums.