Superb tone indeed. Line 6's modeling on the GP and X3 series is really superb.
If he has metal shop it'll be one of these
Bomber Uber Bogner '02 Uberschall
Connor 50 Cornford '03 mk50h
Deity Lead Diezel '03 VH4-Lead
Deity's Son Diezel '03 Herbert
ANGEL P-Ball ENGL® '02 Powerball
Brit Silver Marshall® '87 Silver Jubilee
Brit J-900 Cln Marshall® '92 JCM-900-Clean
Brit J-900 Dst Marshall® '92 JCM-900-Dist
Brit J-2000 Marshall® '03 JCM-2000
Diamond Plate Mesa/Boogie® '01 Triple Rectifier®
Criminal Peavey® '02 5150 II
I would put my money on the Diamond Plate rectifier since he's gone for a Metallica tone, but I could be wrong. :D
Amazingly it isnt the rectifier its a combination of two tones.
The marshall Silver Jubilee panned hard left and hard right for the main tone and the chunkiness (sounds awful on its own)
Then the Line6 Big Bottom also panned hard left & right but a bit quieter to fill it out and add more bite and the high gain (i basically used this amp as a tubescreamer
there are 4 guitar tracks in total, one of each amp either side.
And cheers for the comments on the tone guys.