I like so many different kinds of metal it's silly, but I have pretty wide musical tastes all together. But if I where to single out some favourites I'd have to say:
Thrash - Early Metallica, Megadeth, Anthrax etc
Prog - Dream Theatre, Liquid Tension Experiment, maybe Opeth comes into this list
Experimental - Sikth, Tool, etc
Just to name a few....
I like metal for different reasons depending on which band / genre your talking about at the time, so here goes :
Thrash - Because it's balls to the wall metal, great to listen to when your in a bad (pissed off) mood, also great to put on when your playing FPS's.
Prog - I just love how technical they are, the harmonies can be compared to classical music and it's just really interesting to listen to, especially coming from a guitarist's point of view.
Experimental - Similair to prog really, but quite often it's interesting in different ways, like just the overall sound, almost like soundscapes if that makes sense.