You need welding electrodes to make welded joints. This additive material is available in different forms, depending on the welding technique you use. So you have the coated electrode, welding wire for TIG welding and welding wire on a reel to place in a MIG / MAG welding machine. In addition to the welding technique, when purchasing electrodes you also pay attention to the material and the diameter. To weld a steel sheet of 5 millimeters thick you need a different type of electrode than to connect aluminum 1 millimeter thick.