#1
I'm currently trying to play Metallica - Master Of Puppets and I can play the intro, but my right hand eventually gets sore and I can't continue. Anybody know how I can improve my stamina while downpicking fast.
#2
Martin Goulding is very good. He runs the rock guitar syllabus at a music college I attended. Perhaps a bit robotic in the way he speaks, and personally I don't like his consistent wide vibrato that you'll see on his other videos, despite it being stylistically correct. But he is very good.

This video will explain everything for metal rhythm playing. Pay attention.

https://youtu.be/0EW-JZOcULA