Slayer: Heavy Metal or Heaviest Metal?

In the past few months or so, I've been getting into metal more and more. However, the line between terrible metal and amazing metal is thinner than Louise Brooks's negligee. (if you understand the reference, you might be my hero). However, I like many before me have come to the conclusion after meticulous research that the band Slayer is the heaviest of them all. The music is just so brutal that it makes you either want to die or just punch everyone you see. This is a good thing, as much of Slayer's work is pretty awesome, particularly the album "Reign in Blood", which is widely praised as one of the greatest metal albums ever, if not the greatest. Here's a video of "Raining Blood" (possibly NSFW, definitely amazing) that defines what heavy metal is supposed to be.