Home/Technical Glossary/MIG Welding MIG Welding What does MIG stand for in welding? Metal inert gas. Gas metal arc welding (GMAW), also known as MIG (metal inert gas) welding or MAG (metal active gas) welding, is a process in which an electric arc forms between an electrode and a metal workpiece, heating the metals and causing them to melt, and be joined. The weld area is generally protected from atmospheric contamination by use of an inert shielding or cover gas (argon or helium).