People here seem to have very different attitudes to what constitutes heaviness. A lot of people seem to tie it in with brutality, but for me heaviness is a crushing weighty feeling accompanying every part of a song, something that's absent from a lot of brutal death, which is more of a pulsing onslaught of sound (obviously not so much in the breakdowns and whatnot). That's why I find the heaviest metal to be something like The Abominable Iron Sloth, where every note hits you with crushing force as opposed to something like Wormed.