Gas metal arc welding (GMAW), sometimes referred to by its subtypes metal inert gas (MIG) and metal active gas (MAG) is a welding process in which an electric arc forms between a consumable MIG wire electrode and the workpiece metal(s), which heats the workpiece metal(s), causing them to fuse (melt and join). Along with the wire electrode, a shielding gas feeds through the welding gun, which shields the process from atmospheric contamination.
An electrical arc between the wire and base metal generates heat that melts. Shielding gas protects the molten weld pool from harmful atmospheric gasses.
GMAW most commonly uses a constant voltage, direct current power source, but constant current systems and alternating current are usable.