It can also sound like early thrash, Alice Cooper, Steven Tyler, Phil Anselmo...
The point is to get that 'edge' by being loud enough to make your voice go from the typical 'natural' sound to aperiodic vibration, which is what will be percieved as that bit of 'heat'.
I should note that I recently went to a voice specialist after having a few months of acid reflux issues that were interfering with my voice, and found that if you use the techniques you'll hear as being the 'safe' way - i.e. false vocal folds being stressed, to 'save' the true vocal folds - you can still fuck up your voice because your idea of the 'normal' way to speak and sing will change and you'll be left with what is for all practical intents and purposes an aperiodic voice. I found that (apart from having digestive enzymes all around my voice area) I hadn't taken any hits as far as range goes (I fucked up on the low part of the range test but I know that I've two octaves going straight up from the upper part of my normal speech - and I'm a baritone) and while I have some serious lungs and a powerful enough diaphragm to make people's heads hurt without thinking twice, it did actually change my voice. There is now a substantial gap in the back of the vocal fold contact area - which is normal for women and not harmful to men, but which wasn't there before - and as I mentioned before aperiodicity in my speaking and normal singing voice. Just a heads-up - this is after ONLY going by what several sources confirmed as the 'safe way' and never abusing my voice in any other way.
Jeff