Detected Metals. Metal detectors detect iron, nickel, copper, brass, aluminum, tin, lead, gold, silver and bronze. General-purpose metal detectors can find buried metal objects such as jewelry, coins and other metal objects. "Discrimination" is a process that distinguishes between different metal targets or alloys. Almost all airport metal detectors are based on pulse induction (PI). Typical PI systems use a coil of wire on one side of the arch as the transmitter and receiver. This technology sends powerful, short bursts (pulses) of current through the coil of wire.