So I finally ditched the Death Metal pedal and got a Metal Muff, it's a huge difference. I'm wondering what I should set the amp to...cause I'm new to this stuff and have no clue. I have it plugged into the Low input now.

I play metal, CoB, Amon Amarth, Insomnium, Metallica, Sabbath, Lamb of God, you get the idea.

If your playing high gain stuff I'd use the high gain input rather than the low, as for settings there are way too many tones you are looking for to use one setting. Check the ultimate setting thread for some suggestions for the bands your looking to get.