Welding rod, or electrode, is a metal wire with a flux coating that creates an arc to melt and fuse base metals, serving as a filler metal and providing a protective gas shield. Its purpose is to produce a strong, clean bond by supplying molten metal and shielding the weld area from atmospheric contaminants like oxygen and nitrogen. The flux also helps stabilize the electric arc and removes impurities, resulting in stronger, more uniform welds.