Voltage and current between metals

Copper (wire, Cent coin), iron and zinc (weights for wheels of cars), aluminium (closure of a soft drink can) and magnesium are used as electrodes of Galvanic cells.
A salt solution inside the stopper of an infusion bottle is the electrolyte. The surface of thumbs and forefingers are also used as electrolyte. Voltage and current are measured with a digital multimeter.