Sum 41 is a pop punk rock band from Ontario, Canada, formed in 1996 by vocalist/guitarist Derryck Whibley and drummer Steve Jocz. They were soon joined by lead guitarist Dave Baksh and after a set of bass guitarist they finally settled on Jason "Cone" [=McCaslin=] in 1999. Their first album (''All Killer, No Filler'') was released in 2001 and spawned their most successful single, "Fat Lip".

Their follow-up album ''Does This Look Infected?'' was released in 2002. It featured a darker sound and also more serious lyrical themes. This continued onto their third album ''Chuck'', released in 2004. In 2006, Baksh left the band to focus on his own band Brown Brigade. He was replaced by Tom Thacker, who was initially only a live member, while their 2007 album ''Underclass Hero'' was recorded as a trio. Thacker became an official member in 2009 and helped to co-write title track for their fifth studio album ''Screaming Bloody Murder'', released in 2011. However, that album (along with ''Underclass Hero'') had all guitar parts performed by Whibley.

The bandís music is primarily pop punk and punk rock, though they have diversified over the years. They moved from pop punk (with some rap rock) on ''All Killer, No Filler'', to melodic hardcore on ''Does This Look Infected?'' and ''Chuck'' (with the latter having alternative metal influences and lighter alternative rock), back to pop punk with ''Underclass Hero'', and back to melodic hardcore with ''Screaming Bloody Murder''.

Sum 41 currently consists of Whibley on vocals and rhythm guitar, Tom Thacker on lead guitar and backing vocals and Cone on bass and backing vocals. Drummer Steve Jocz left the band in April of 2013, leaving Derryck as the sole remaining founding member. Jocz replacement has not been announced yet.

* "Half Hour of Power" (2000, EP)
* "All Killer, No Filler" (2001)
* "Does This Look Infected?" (2002)
* "Chuck" (2004)
* [[LiveAlbum "Go Chuck Yourself"]] (2005, released in Japan as Happy Live Surprise)
* "Underclass Hero" (2007)
* [[GreatestHitsAlbum "All the Good Shit"]] (2008)
* "Screaming Bloody Murder" (2011)

!They provide examples of the following tropes:
* AllDrummersAreAnimals: Steve.
* AlterEgoActing: As Pain for Pleasure (see below). Also in music video for Still Waiting, they performed as The Sums and were renamed. Derryck was Sven, Dave was Holmes, Steve was Sergio and Cone was Thurston.
* AscendedExtra: Tom, as of 2009.
* CountryMatters: A.N.I.C., which stands for Anna Nicole Is (a) Cunt.
* DarkerAndEdgier: Does This Look Infected? was this to All Killer, No Filler and Chuck was this to Does This Look Infected and finally Screaming Bloody Murder is this to Underclass Hero.
* ExactlyWhatItSaysOnTheTin: Half Hour of Power, although it's actually slightly shorter, with the 30 minutes length being only done with added silence after the last song.
* ExecutiveMeddling: Parodied in Still Waiting music video. At the start, their record label executive (portrayed by Will Sasso) renames the band and its individual members, stating that "number bands are out" and ""the" is in". It also parodies the executives' (supposed) lack of knowledge about music and musicians with Sasso saying, that although he has "not heard the new album, it's probably all sorts of songs about skateboarding and [[BreakupSong getting dumped]]" and stating band names like [[Music/GreenDay Green Day 75]] or [[Music/LedZeppelin The Led Zeppelins]].
* GenreShift / NewSoundAlbum: See above.
* HeavyMetal: They had an AlterEgoActing band named [[FakeBand Pain for Pleasure]], where they performed in wigs and costumes and used nicknames - Steve (who was lead vocalist here) was Pain, Derryck (drummer) was Gunner, Dave was Pleasure and Cone was Sniper. They recorded three songs under this monicker: Pain for Pleasure, Reign in Pain and WWVII Parts 1 & 2. They also appeared as this in two of their music videos: Fat Lip (where they performed their self-titled song) and We're All to Blame (where they were announced as next band to perform on Solid Gold). Incidentally, Derryck is shown as guitarist in both of those appearances, although he actually played drums in this band.
* ImAHumanitarian: In one of their web videos, Basketball Butcher, after losing against Cone in basketball match, Steve kills him and then cooks him. Later, Derryck and Dave come in. They ask him what is for the dinner. Steve replies with "You!".
* PunkRock
* RapRock: Fat Lip and What We're All About.
* RockTrio: During Underclass Hero era they officially consisted only of Derryck, Cone and Steve (Tom was a live member only and as such did not play on the album, nor did he appear in music videos). Screaming Bloody Murder was also recorded in three piece.
* SpecialGuest: [[Music/{{Slayer}} Kerry King]] on [[Film/SpiderMan What We're All About]].
** Sum 41 themselves performed on Little Know It All by [[Music/TheStooges Iggy Pop]] and Get Back by Ludacris.
* StartMyOwn: Dave Baksh, who left to form Brown Brigade.
* StepUpToTheMicrophone: Aside from singing on Pain for Pleasure songs, Steve also rapped on Fat Lip, What We're All About and Thanks for Nothing (along with Derryck and in case of first two, Dave).
* TheSomethingSong: The Hell Song, Exit Song
* ThrowItIn: During the making of music video for Pieces, Derryck walks across various trucks that spot slogans such as "The perfect family", "The perfect body" or "The perfect night". At the end of the video, he himself is in one such truck that reads "The perfect life is wating for you". Then the F in life falls off, changing the line to "The perfect lie is wating for you". While this was an accident, they decided to leave it there, as they thought if fit the mood of the song.
* TrashTheSet: The end of Still Waiting video. Also in Walking Disaster.
* WarIsHell: Still Waiting.