Sum 41 is a Canadian punk rock band from Ajax, Ontario, Canada, active since 1996. The current members are Deryck Whibley (lead vocals, rhythm guitar), Jason McCaslin (bass guitar, backing vocals), and Tom Thacker (lead guitar, backing vocals, keyboard). They've released five studio albums. The band released their debut album, All Killer No Filler, in 2001. The band achieved mainstream success with their first single from the album, "Fat Lip", which reached number-one on the Billboard Modern Rock Tracks chart and remains the band's most successful single to date.