Join the two pieces of thin metal together and clamp them together, if necessary. Avoid gaps between the sheets of metal which will lead to warping.
Attach a backing bar to the back of the thin metal. The backing bar acts as a heat sink and will absorb the heat disseminated by the welding tool.
Strike the welding electrode on the thin metal to form an arc. Allow the arc to melt the metal, forming a welding puddle of molten metal.
Move the welding tool along the surface of the thin metal extending the welding puddle. Aim the arc at the center of the welding pool, allowing the pool to best shield the thin metal. Travel in a straight line, instead of whipping or weaving the tool around, which will cause an excessive heat-affected zone.