The biggest concern you will have with bonding metal is making sure the metal is not containing any water. Most metals are porous and will absorb moisture from the air.
When you utilize an epoxy adhesive, the resulting chemical reaction will create a small amount of heat. This heat will condense the moisture on the surface of the metal and the epoxy will then bond to a layer of moisture instead of bonding to the metal.
This will seriously weaken the bond joint to the point where the epoxy will eventually fail on the metal surface.
If you take a torch to the surface of the metal, you will generally see the moisture evaporating from the metal. You can either use a torch on the metal or you can heat the metal pieces up enough to evaporate the moisture. This will ensure that you have a clean surface for the epoxy to bond to the metal.