GMAW process. Gas metal arc welding, sometimes referred to by its subtypes metal inert gas and metal active gas is a welding process in which an electric arc forms between a consumable MIG wire electrode and the workpiece metal, which heats the workpiece metal, causing them to fuse. GMAW is a welding process which joins metals by heating the metals to their melting point with an electric arc and the arc is struck between a continuous, consumable bare (not covered) electrode wire and the work pie