The mechanisation of welding is divided into four levels according to the proportion of work stages done mechanically with a welding machine

In MIG/MAG welding, an arc is created with the power supply through the welding gun between the welding wire being fed and the work piece. The arc fuses the material being welded and the welding wire, thus creating the weld. The wire feeder continuously feeds welding wire through the welding gun throughout the welding process. The welding gun also provides shielding gas to the weld.

The shielding gas often plays an important role in the productivity and quality of welding. As its name suggests, the shielding gas shields the solidifying molten weld from oxygenation as well as impurities and moisture in the air, which may weaken the corrosion-tolerance of the weld, generate porous results and weaken the durability of the weld by changing the geometrical features of the joint. The shielding gas also cools down the welding gun.

There are several risk factors connected to welding. The arc emits extremely bright light and ultraviolet radiation, which may damage the eyes. Molten metal splashes and sparks can burn the skin and cause risk of fire, and the fumes generated in welding can be dangerous when inhaled