Himeaimichu

  The heaviest Metal band in the world is Fear Factory. I mean, look at that guitarist! All the members combined weight with him is pretty heavy. Probably about a few thousand pounds at most.

  Oh, you mean heavy in guitar? Well, early Dir En Grey used an ESP Ganesa, which is a big guitar that weighs a lot. 
Pretty heavy. So heavy, they switched to SG clones

  Wait, you mean heavy in tone? As in Amps? Well, most Metal band use valve amps, combined with big cabinets, which weigh a lot. 
So.. IDK who to choose there

  Oh, you mean heaviness in sound? Well, soundwaves don't really have mass, but higher frequencies have more air particles close together, so... 
*Pulls out an oscilloscope* This is gonna be a long one