In electrical, chemical, and industrial applications, electrodes are generally classified into distinct functional categories based on their material composition and reactivity. The four primary classifications include graphite and carbon electrodes (used heavily in metallurgy and electric arc smelting), metal electrodes (such as copper, steel, or platinum used in welding and electroplating), composite electrodes (combining various conductive materials for sensors), and inert or sacrificial electrodes used in electrochemical cells.