Alot...
Edit: After a "quick" count. 381 Albums. 255 singles. 15 (only!) DVDs, 34 LP records, 12 record singles (all Iron Maiden)
95% of them are power/melodic/prog/symphonic/newer heavy metal. The remining percentage is made up from all the "classic" stuff, NWOBHM, old thrash. (Old Metallica, Maiden, Megadeth, Priest, Motorhead, Ozzy, etc etc.)
I have a few Folk metal albums aswell, Korpiklannai, Turisas, Ensiferium, Battlelore, that kind of stuff, but they are the closest thing to black metal I have.
To be honest I've never been to keen on Death/Grindcore kind of metal, not that its too extreme, I just prefere songs with melody and lyrics that I can sing along to without having to have the book open infront of me
I tend to become obsessive with "collecting them all," (pokemon anyone?
) and own entire discographys, singles and EPs to boot. It does leave a hole in your pocket, as does frequent merch and gigs, but I wouldn't swap my collection for the world
I have no Emo or Nu-Metal.