Alright, well first off, I'm not quite sure of the terminology, for me all "Metal vocals" are screams.

Anyways, this is what I want to do: You know those crazy low screams that make you go "Holy fuckballs, that's just about as low as my bass in drop C!", well I want to learn how to do those.

Right now, when I try to do a low scream it just sounds like I'm sitting on the shitter trying to force out a turd, but what I want to sound like is something like Born of Osiris, the low screams from The Black Dahlia Murder, Suicide Silence, That part in the Carnifex song "Lie to my face" Where he goes "Lie to my......... FEEEEEUUUUUUUUCEEEEEEEEE. You know what I'm talkin about.

So anyways, if anyone would like to explain to me how to do those, or something similar to those, it would be very appreciate, and thanks in advance.

basically, i think you mean gutturals. the way to do them isn't with your voxal chord. push air up through your throat with your diaphragm, you should feel the rumble in your chest for lows and your false chords for highs. you can also cup the mic to get that drop c bass low if you want, though some people frown upon it (i think its fine, just like palm muing on guitar and other techniques)

Dude great tips. I can't manage it either, I just can't get that low...but props if you can manage it