Green Day is a musical group.
Green Day is an American punk rock band formed in 1986 by lead vocalist and guitarist Billie Joe Armstrong and bassist Mike Dirnt . For much of the group 's career , the band has been a trio with drummer Tré Cool , who replaced former drummer John Kiffmeyer in 1990 prior to the recording of the band 's second studio album , Kerplunk ( 1991 ) . The band 's rock opera , American Idiot ( 2004 ) , reignited the band 's popularity with a younger generation , selling six million copies in the U.S. . The group has won five Grammy Awards : Best Alternative Album for Dookie , Best Rock Album for American Idiot , Record of the Year for `` Boulevard of Broken Dreams '' , Best Rock Album for the second time for 21st Century Breakdown and Best Musical Show Album for American Idiot : The Original Broadway Cast Recording .