The fusion of metals by controlled heat (electricity) and, in some cases, pressure or force. A high-density current is applied for a given length of time to produce the heat required to join two metal components into a single assembly. Typically, the electrode at the tip of the welder conducts the electricity and furnishes the pressure or force to center the current flow at the desired welding point. A weld's characteristics depend on the size, shape, and other key properties of the electrode. The contour of the electrode changes as the usage increases and if not continually dressed (reshaped) to the original or desired size, the weld itself changes physically and can weaken.