Depends alot on the budget. Any brand of amp can pull off a metal tone really. You really gotta get your son out there to try some stuff out. Also, are you looking to get a big combo amp, or a stack? I would say if you can't spend alot check out some of the lower end harkte and ashdown stuff. SWR also has some reasonably priced stuff. SWR, in my opinion, has some really great stuff for the money. If you want to spend more you could check out ampeg, mesa, sunn, fender and some higher end SWR stuff. Ampeg is always a good choice, its all I use. Mesa and the higher end SWR amps and cabs are really awesome too. I owned a Sunn 1200s for a while. It was a monster 2-channel amp, clean and overdrive. That would be a great head for metal.