MIG (metal inert gas) wire provides filler metal for GMAW (gas metal arc welding) tasks. Also known as welding wire or filler wire, this solid wire requires external shielding gas to keep contaminants out of the weld pool. It comes on a coil or spool and is fed through a compatible welding gun. An arc is created between the wire and a workpiece, and the heat from the arc melts and fuses material from the workpiece and the wire to create a weld.