You will get a far superior metal tone from the amp than using the pedal (IMO). Try keeping the gain down to an absoulte max of 7 - 6 is better. BElieve ot or not but you will get a lot more clarity and definition thus a far heavier tone from lower gain settings. Depends entirely on your pickups and techniquem but a good tone from my MG100DFX is: bridge humbuckers, gain 6.5, treble, 8, mid 9, presence 6, volume 10, master volume to whatever your ears can take. The same setting off the neck is excellent for shred solos, very thick and creamy with good clarity. Also if you nudge the master volume you can get good controlled feedback.
You can get some pretty good death metal tones from the MT-2 but when it comes to finding a signature tone or something that you would actually think about having on a cd it falls short, to my ears anyway. Lots of guys like them, I have one and used to think it was cool for getting badd ass over saturated tones but now I prefer heavier clearer tones from less gain.