Armor of Voltage

You touch a willing creature who is wearing no or light armor, and a protective magical force surrounds it until the spell ends. The target's base AC becomes 13 + its Dexterity modifier. Whenever the creature hits or is hit with a melee attack it may have a creature within 5 ft of it make a Dexterity saving throw. The target takes1d4 lightning damage on a fail or no damage on a successful save. The target automatically fails the saving throw if they are wearing metal armor. The spell ends if the target dons medium or heavy armor or if you dismiss the spell as an action.