 Having sold about 38 million units worldwide, Megadeth is one of the few bands from the 1980s American underground metal scene to have achieved mass commercial success.Along with contemporaries Metallica, Slayer, and Anthrax, Megadeth is regarded as one of the core founding groups of thrash metal.These bands are often referred to as the "big four" of thrash metal, responsible for the genre's development and popularization.