Metallica, an iconic American heavy metal band, was formed in Los Angeles in 1981 by vocalist/guitarist James Hetfield and drummer Lars Ulrich. Known for their fast tempos, intense instrumentals, and aggressive style, they became one of the "big four" bands that defined thrash metal, alongside Megadeth, Anthrax, and Slayer. Now based in San Francisco, the band's lineup includes Hetfield, Ulrich, longtime lead guitarist Kirk Hammett, and bassist Robert Trujillo. Over the years, past members have included guitarist Dave Mustaine—who later founded Megadeth—and bassists Ron McGovney, Cliff Burton, and Jason Newsted.