Metal Detector is a Normal Trap Card.
Trap Cards are normally Set first and can be activated on a later turn, often in response to an action.
On the current TCG and OCG Forbidden & Limited lists tracked here, Metal Detector is Unlimited.
YGOPRODeck lists Metal Detector for these formats: GOAT, OCG GOAT, Duel Links, Common Charity, Edison, TCG, OCG, Master Duel.
A listed print of Metal Detector appears in Pharaoh's Servant (PSV-022) at Common rarity.
Among markets shown on this page, the lowest listed snapshot for Metal Detector is about $0.02 on Cardmarket (prices change frequently).
