This is one of the most common types of welding. As in Manual Metal Arc (MMA) the joint interface and electrode melt, under intense heat created by electric current, this forms a weld pool. This rapidly solidifies to form a bead of weld metal. MIG welding uses a shielding gas to protect the molten weld pool from the atmosphere and encourages the formation of a good weld. MIG is also well suited to automated manufacturing systems.
The following image demonstrates how ‘Gasless’ MIG welders operate. In this instance there is a special coating over the consumable wire. When the Arc is created the energy involved converts the wire coating into the gas that ‘pushes’ oxygen away from the weld.