I have silicon carbide in mine use it to clean up metal - like diff yokes, its pretty harsh. it depends on what kind of metal your cleaning. I dont blast alot of stuff but an older buddy used to do lots of aluminum intake manifolds with actual glass beads - they have several grades after doing thefirst blast he would change the glass and vacuum it out-put in new glass and blast again- the final surface looked really sweet. so try out different ritueals it just depends how nice you want it to look.