Gas metal arc welding (GMAW), sometimes referred to by its sub types metal inert gas (MIGwelding or metal active gas (MAGwelding, is a welding process in which an electric arc forms between a consumable MIG wire electrode and the work piece metal(s), which heats the work piece 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 atmospheric contamination.The process can be semi-automatic or automatic. 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……..Wikipedia