Metal inert gas(MIG) welding, also known as Gas metal arc welding(GMAW) or metal active gas(MIG)welding, is a welding process in which an electric arc forms between a consumable wire electrode and the workpiece metal(s),which heats the workpiece metal(s), causing them to melt, and join. Along with the wire electrode, a shielding gas feeds through the welding gun,which shields the process from contaminants in the air. The process can be semi-automatic or automatc.A constant voltage, direct current power source is most commonly used with GMAW,but constant current systems, as well as alternting current, can be used.

GMAW is the most common industrial welding process, preferred for its versatility, speed and the relative ease of adapting the process of robotic automation.Unlike welding processes that do not employ a shielding gas,such as shielded metal arc welding, it is rarely used outdoors or in other areas of air volatility.A related process, flux cored arc welding, often does not use a shielding gas, but instead employs an electrode wire that is hollow and filled with flux.