Don't think the tube screamer would be what you expect, it's barely a medium gain OD, gets a bit muddy in the lows, but it can sound magical when set right. I always thought it was popular with the metal fraternity because of the mid hump in it that lets it cut through (mind you, it was just putting back in what the metal guys where scooping out with the mid control), and that because it's medium gain it boosts properly without turning into an over compressed mush.
So it's not really a "metal pedal" just a pedal that metal guys used. I think the things like the HM-2 and MT-2 (had one of them years back, don't remember which) get used because they have fairly powerful eq controls and can be used to get some pretty extreme sounds. I never thought the actual distortions on them were up to much. but then again, I'm not looking to get "that" sound, one mans noise is another music and all that.
