Megadeth is a thrash metal band from Los Angeles, California. The group was formed in 1983 by guitarist Dave Mustaine and bassist David Ellefson, shortly after Mustaine's dismissal from Metallica. A pioneer of the American thrash metal scene, the band is credited as one of the genre's "big four" with Anthrax, Metallica and Slayer, responsible for thrash metal's development and popularization. Megadeth plays in a technical style, featuring fast rhythm sections and complex arrangements; themes of death, war, politics and religion are prominent in the group's lyrics.

In 1985, the band released its debut album on the independent label Combat Records. The album's moderate commercial success caught the attention of bigger labels, which led to Megadeth signing with Capitol Records. The band's first major-label album, Peace Sells... but Who's Buying?, was released in 1986 and greatly influenced the underground metal scene. Despite the album's prominence in thrash metal, frequent disputes between its members and substance abuse issues brought Megadeth negative publicity during this period.