legit, sum 41 is maybe in my top 5 artists, and i realize there are a shit ton of more talented bands out there, but "crash" alone changed who i am as a singer. like the way he annunciates "time" and especially "goodbye" in the first verse is a perfect example of this. the vibrato-ish effect he puts into those ending notes is just beautiful and definitely comes from the chest and torso moreso than the throat. like when i sing in that fashion, i find myself twitching a bit (kinda like how kobiashi does while eating hot dogs if that makes sense). also, it's def important to sing w/ some swagger. brad nowell taught me that. like listen to this part at about 1:30 when he says "ain't no waaaaayyyy, no way to shop," he just puts so much badassery into that line.
the truth is there's no right and wrong way to sing (save rebecca black), just whatever you do, try to sound unique.