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.
Sum 41 released their debut album, All Killer No Filler, in 2001 and achieved mainstream success through the album's first single, "Fat Lip", which reached number-one on the Billboard Modern Rock Tracks chart; it remains the band's most successful single to date. They have since released four more studio albums: Does This Look Infected? (2002), Chuck (2004), Underclass Hero (2007), and Screaming Bloody Murder (2011).
The band was formed by singer-songwriter Deryck Whibley and drummer Steve Jocz, after Whibley convinced Jocz to join his band. Jocz was a drummer in another band and Whibley was convinced that "he was the best drummer around". The duo then added Dave Baksh as lead guitarist a year later and after going through several bassists, ended up picking jason McCaslin to complete their lineup.
On May 10, 2006, Dave Baksh announced in a statement through his management company that he was leaving Sum 41 to work with his new band, Brown Brigade, which has a more "classic metal" sound. Baksh cited "creative differences" as the reason for his departure but claimed that he was still on good terms with the band. On March 9, 2010, Steve Jocz confirmed that new lead guitarist Tom Thacker will take part in the writing and recording.
On April 18, 2013, drummer Steve Jocz announced he would be leaving the band via his official Facebook page, leaving Whibley as the sole founding member of the band. Their follow up album will be the band's second collaboration as a trio and first with Whibley and McCaslin as the only two bandmates from their original release left.