They have 5 albums. In them, Sum 41 has a different sound in each album. Their 2nd album is pop-punk with a little alt metal. Their 3rd album has 2 punk songs amidst melodic hardcore, alt metal, metal, and 2 quiet songs, the band cited Metallica as an influence for this album. (They have also played a full length Master of Puppets cover.) The bands 4th album went back to their roots, stripping the metal influence. This album is pop-punk. Their 5th album is closer to a sequel to their third, with much louder vocals and much better instrumental parts. It is an alt metal/alt rock album with punk influence. Their third and fifth albums also have many shifts from soft to loud within songs. They have songs that include all 4 members on vocals, and utilize a lot of vocal harmony.
Basically, this band isn't groundbreaking most of the time, but they go into a lot of music and pull it off well. Most people write them off due to their first album or think they are copying Metallica, Oasis, Green Day, Blink-182, Linkin Park, etc.
They never claimed to be 'punk' so all you petty losers can stop your bitching.
Just because a band has an army of teeny fans doesn't detract from the fact that their music is actually...pretty damn good.
It's number 32 now here's the situation
if the beat moves ya feet then
dont change the station
pack ya bagz cuz we leavin on a perminent vacation
well im a disaster
a microphone master
its time to rock ya ghetto-blaster
its not about the cars, money, hotels, or resorts
bout sweatin all the bitches in the biker shorts
and im dave brownsound can ya see me runnin late
imma make ya girlie feel great