I tried to cover the spectrum as much as possible with regards to rhythmic playing style from one record to the next. This first riff is rather ala "Death Magnetic". The main thing to keep in mind when playing this riff, is the picking directions. This will be emphasized greatly throughout this tutorial - achieving the machine gun-like qualities of Metallica riffs through means of down-picking. Each and every eighth note is down-picked, the only exception is quick 16th note bursts. Focus closely on the demonstration video and be sure every down and up-beat are played downwards.