Magical Arm Shield 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, Magical Arm Shield is Unlimited.
YGOPRODeck lists Magical Arm Shield for these formats: OCG GOAT, Duel Links, Common Charity, Edison, Speed Duel, TCG, OCG, Master Duel.
A listed print of Magical Arm Shield appears in Battle Pack 2: War of the Giants (BP02-EN186) at Common rarity.
Among markets shown on this page, the lowest listed snapshot for Magical Arm Shield is about $0.10 on Cardmarket (prices change frequently).
