Heat is about the only way you'll get it off...Want to heat the calliper (disc brakes) / wheel cylinder (drum brakes) more then the bleed screw...this will expand the metal around the bleed screw and should be good to get the screw to move with the vice grips. Worst case scenario, you'll have to heat the brake line (unless they are new), remove it and then remove the calliper / wheel cylinder and do it on the bench. Sometimes it's easier and way less frustrating to just replace it all with new parts (when you can afford it) and start from there. All the brake components work then. I live in the north and everything rusts up and gets seized. Done this job lots of times on various vehicles.
you don't need a big cutting torch and a propane torch may work...heat combined with shocking the metal with a cold wet rag will also help too. Sometimes I have done several combinations of things.
