Gas metal arc welding (GMAW), sometimes referred to by its subtypes metal inert gas (MIG) welding or metal active
gas (MAG) welding, is a semi-automatic or automatic arc welding process in which a continuous and consumable
wire electrode and a shielding gas are fed through a welding gun. A constant voltage, direct current power source
is most commonly used with GMAW, but constant current systems, as well as alternating current, can be used. There
are four primary methods of metal transfer in GMAW, called globular, short-circuiting, spray, and pulsed-spray, each
of which has distinct properties and corresponding advantages and limitations.