If we are talking about Hetfield here;
KEA = Jose Arrendondo Modified 100 watt Marshall SLP
Pro Co Rat Distortion Pedal
Marshall 4x12
White Flying V Copy (passive
RTL = Replacement 100 watt Marshall Heads that were later modified (KEA originals stolen)
Ibanez Tube Screamer-Last time James used an overdrive/distortion pedal
Marshall 4x12
White Flying V Copy
White Gibson Explorer EMG
MOP = Mesa Boogie Mk IIC+
Mesa Boogie Quad Preamp
Marshall JCM 800
Marshall JMP Heads
Marshall 4x12 with 65 watt speakers
Furman PQ4 parametric EQ
Ibanez multi-effects box
Mesa Boogie Heads slaved into Marshalls
White Gibson Explorer EMG
White Flying V Copy
AJFA = Mesa Boogie Mark IIc+
Mesa Boogie Quad Preamp
Marshall JMP/JCM Heads
Roland JC120 Combo
Marshall 4x12
Mesa Boogie 4x12
Mesa Boogie Heads slaved into Marshalls
White Gibson Explorer EMG
2xWhite and 1xBlack ESP Explorer
Marshall 4x12 cabs all use Celestion Vintage 30's!
Also, on AJFA, James 'scoops' his mids alot more than usual (as, contrary to many beliefs he is not a 'heavy' scooper.
This is all studio eqpt.
Dare say with pedals may get close but KEA had heavily modded Marshall heads and 'most' of perceived Tallica tone is pure 'Mesa' tone.
Mesa, being rather costly, esp. for what he used/uses (a ROV does the job nicely though) a Mesa pedal 'may' work;
like a Mesa 'V twin' if you can find one.
Apart from that, a modellor I guess.
Having played and now owning a Mesa I have to say they have a VERY distinctive tone and hitting it without digital effect (modellor) or real thing may be tricky.
Sorry, hope ya get close though.
BTW, Have an ENGL Screamer half stack (pedals, HBE) and 10 band EQ and cannot replicate the tone of the Mesa Rectifier (so this may be one to knock off list).