Metallica is an American heavy metal band formed in Los Angeles in 1981 by vocalist and guitarist James Hetfield and drummer Lars Ulrich, and later based primarily in San Francisco. The band is regarded as one of the leading acts in thrash metal, alongside Megadeth, Anthrax, and Slayer. Its core lineup has long consisted of Hetfield, Ulrich, lead guitarist Kirk Hammett, and bassist Robert Trujillo. Former members include Dave Mustaine, who later formed Megadeth, and bassists Ron McGovney, Cliff Burton, and Jason Newsted.