Mastodon is an American heavy metal band formed in Atlanta, Georgia, in 2000. The core lineup for most of the group’s history featured Troy Sanders, Brent Hinds, Bill Kelliher, and Brann Dailor. Their sound has been described as a mix of sludge metal, progressive metal, groove metal, and stoner rock, with occasional hard rock and psychedelic influences. The band’s early releases, including Remission (2002) and Leviathan (2004), helped establish their reputation, and Leviathan is frequently cited as a key metal album of the 2000s. Later albums such as Blood Mountain (2006), Crack the Skye (2009), and Emperor of Sand (2017) expanded their progressive approach. Live, Mastodon are known for complex arrangements, shifting time signatures, and performances that often feature layered vocals and extended instrumental sections.