3) sit vs set
4) raise vs rise
5) can vs may
Can, as an verb, describes the ability of a person to do something or the possibility of something to happen. "He can keep on headbanging long after the little pink bunny gives up." "Can it be that he's actually getting tired?"
Can, as a noun, describes a cylindrical shape with a hollow interior which is usually metal. "He inhaled the can of coffee before it was even opened, so he could keep on headbanging", or a jail, "He headbanged so much that it was illegal, and they threw him in the can", or a toilet, "He headbangs even when on the can", or the ass, "His can must be getting tired from all that sitting.
May, if you ignore its use as the name of a month, is a verb used to denote permission, "May I keep on headbanging, daddy?", possibility, "He may just keep on headbanging until he dies.", desire, "He may want to look at your mongos, but he still ain't gonna quit headbanging", or purpose, "He kept headbanging so that his children may come to respect the power of headbanging over desire"