Metallica is an American heavy metal band. They were formed in October 1981. With 57 million albums sold in the United States, and 40 million albums sold outside the U.S., the total number of album sales is nearly 100 million. The band has become one of the most commercially successful heavy metal acts in history. After building a following through its role in the development of modern heavy metal, in the mid-1980s, the band broadened its audience in the early 1990s.