You can’t go wrong with Sepultura or Pantera. If you haven’t heard of Testament then go pick some up, it is some good stuff to listen to while lifting they are all good but I favor “Low” over them all.IF you are really hardcore though, go pick up Carcass “Heartwork”, that album is one of the best in the world and it will make you want to do more that just lift, it’ll makw you want to beat the hell out of somebody and that will make you even more pumped for lifting.