If you're still adjusting the knobs and wanna get really authentic... Metallica usually set their amps as such, historically speaking:

Volume would be adjusted based on venue but might as well go 10 for this, Bass 7, Mid 3, Treble 8, Gain 7. They basically perfected the scooped mids sound that still dominates most rock and metal today. For the clean channel (top right set) pull the bass back to about 4 and raise the mids to 4. Also, the knob labeled RVB Clean on the far left, turn that to 2 or 3. That'd be the reverb for the clean channel and they use just a touch of it. Probably turn the Reverb Crunch down half from where it is, if not all the way.

Last, turn the top two Master knobs to 8. That'd be the master volume that overrides all the individual channel volumes. There's no way to know the EXACT settings they used, and they should change a little show to show based on the space, but these capture the spirit of what their settings were (are) and I'd bet they're within .5 to 1 of what the settings actually were.