Metallica guitar lesson. Arpeggio crazy excerpt from Kirk Hammet solo.

Also, remember that if you can't play the riff at the actual speed Hammet plays it at right away, don't give up. It's much more important to understand the riff and be able to apply the riff in actual musical situations. That means understanding where it comes from and where it can be used and being able to play it at many speeds.

Speed is simply repetition and lots of it. The hard part is learning and using the right fingers and the right picking pattern. Always be consistent with your fingering and picking patterns. Once you have this part down, dig out your metronome or buy one and get yourself a calendar. Each day play the riff at a tempo where you can play it at a least 5 times in a row without a mistake. Mark that tempo on your calendar. Next day, review the tempo you did from the previous day and then push it forward a notch or two. If you can successfully play at the new tempo 5 or more times in a row, write that on your calendar. If not write the same tempo on your calendar.

Please note: Your speed will grow in spurts. You may move one or two notches on the metronome every day for a week and then get stuck at a tempo for a week or sometimes longer. Stay consistent. Be patient. Don't give up. You can play as fast as you want providing you are willing to work a little.