It really depends on the band and subgenre. Traditional metal, doom metal, power metal, and most progressive metal use more conservative clean vocals. Thrash metal uses bellowing not unlike punk music. Death metal isn't so much screaming as it is growling (not the same thing). Groove metal sometimes mixes harsh vocals with clean vocals, but it depends on the band. The only subgenre that comes close to "screaming" is black metal and it's not so much screaming in the "screamo" sense, but in a harsh vocal sense.
I can't remember if metal includes screaming like screamo does, but I know I'm not fond of screaming. (so that's why I didn't listen to it to see if it was metal or not) If it's not, I'll listen to a few songs! I always like getting new music :D
Wow, that sounds pretty intense! (to get you to throw your keyboard!) That's a big reason I don't venture in there, as people can get really passionate and/or say really ridiculous things making me frustrated etc.