Megadeth is an American heavy metal band formed in Los Angeles in 1983 by guitarist Dave Mustaine and bassist David Ellefson. Along with Metallica, Anthrax, and Slayer, Megadeth is one of the "big four" of American thrash metal, responsible for its development and popularization. Their music features complex arrangements and fast rhythm sections, and lyrical themes of death, war, politics, personal relationships and religion.