The Master of Puppets intro (Metallica) was the first thing I wanted to learn when I started playing guitar a few weeks ago. I hadn't started working on Alternate Picking yet. I just played with downstrokes across all the notes and chords which slows down the execution big time. I have been working on scales with alternate picking. I use alternate picking to play all the new stuff I've learned , but the Master of Puppets bit is stuck in down picking only because that's how I learned it. Over the next day or two I want to play with alternate picking so I can speed it up to the same tempo Metallica uses.
I found this Great Exercise on Guitarists.net. What's nice with that lesson is that it showed me that I have to remember to be efficient with my picking. For example, on the first three notes I was doing Down, Up, then Down for the next string, when I should have been doing Down, Up, then Up again to the upper string. Works for me!