Metallica is an American heavy metal band formed in 1981. They are one of the most commercially successful and influential bands in the history of hard rock and heavy metal music, having sold over 125 million albums worldwide. The band's fast tempos, instrumentals, and aggressive musicianship made them one of the founding 'big four' bands of thrash metal, alongside Megadeth, Anthrax, and Slayer. Metallica has released ten studio albums, four live albums, five extended plays, 37 singles, and 39 music videos.