A Perfect Circle is an American rock supergroup formed in 1999, featuring notable members such as Maynard James Keenan of Tool and Billy Howerdel, a former guitar technician for Nine Inch Nails. Their music style is recognized as a blend of alternative rock, art rock, and progressive metal, characterized by emotional lyrics, complex song structures, and a distinctive, ambient guitar sound. The band's debut album, "Mer de Noms," was a significant commercial success, reaching multi-platinum status and solidifying their role in the early 2000s rock scene. Despite numerous lineup changes and hiatuses, A Perfect Circle remains a significant influence in the rock genre.