How do you get really good feedback
ermmm, dime the gain and stand close to your amp? Also throw in an od pedal with some gain on it also? Also really hot pups?
could u add a metal pedal with some distortion
Volume. None of those other things is really necessary.
Get a nice heavy sound that you like and play for example an 'a' power chord and let it ring out rigt infront of your amp. Or hit harmonics in different places. It varies on many amps. You can hit a pinch harmonic and let it ring out into feedback and then continue to change the pitch of your feedback.
turn every knob on your amp all the way up. seems to work good. :]