After he left Metallica in 1983, guitarist/vocalist Dave Mustaine formed the thrash metal quartet Megadeth. Though Megadeth followed the basic blueprint of Metallica's relentless attack, Mustaine's group distinguished themselves from his earlier band by lessening the progressive rock influences, adding an emphasis on instrumental skills, speeding up the tempo slightly, and making the instrumental attack harsher. By streamlining the classic thrash metal approach and making the music more threatening, as well as making the lyrics more nihilistic, Megadeth became one of the leading bands of the genre during the mid- and late '80s. Each album they released went at least gold, and they continually sold out arenas across America, in addition to developing a strong following overseas. By the early '90s, they had toned their music down slightly, yet that simply increased their following; all of their proper '90s albums debuted in the Top Ten.