Well now, I have seen some thread on this forum saying your equipment doenst make you sound like metallica in your case. So if you would have all Metallica's guitars and amps you would come close, but more important is your technique. And I totaly agree on that.

Im currently running on a Marshall valvestate, setting my distortion channel wide open and bass treble middle @ max
no effects, just the standard marshall distortion.
My BC Rich guitar gives an incredible raw agressive heavy metal sound :) ---> 2 BC Rich BDSM Humbuckers

When I play metallica I dont hear any difference(Espessialy the old albums like And Justice, Master etc).

So I would say Practice like a M*th*r F*ck*r because Jamyz Hetfield aint a pussy playing guitar. He is a truely underrated guitarist.
If your technique is good, and your using fairly good equipment you should be able to get that sound.