I have a stock '70 Super Trem and a stock '72 Super Lead and Metropoulos 12000 series 68 plexi clone and also a Marshall SV20. They are all mean enough to do heavy rock and classic metal tones with a Boss SD-1 or a Graphic EQ in front of them. Mean, tight and crunchy as hell with enough sustain and this punchy, articulate, in your face sound that IMO starts going away the more gain you add.
Do they do modern metal tones? How would I know? lol I'm not interested in that. I have owned 5 or 6 modded Marshalls over the years and had a Morin preamp and for the sound I am looking for, stock Super Leads with a little boost and low end tightening from those pedals just does it.
I don't set my Marshalls for clean. I set them to where they sound like the meanest classic rock sounds bordering on reaching hard rock sounds. Then I give them a little push with the pedal and it is killer.