The Heat Metal spell description says:
Choose a manufactured metal object, [...] Any creature in physical contact with the object takes 2d8 fire damage when you cast the spell. Until the spell ends, you can use a bonus action on each of your subsequent turns to cause this damage again.
[...] If it doesn’t drop the object, it has disadvantage on attack rolls and ability checks until the start of your next turn.
Scale Mail. This armor consists of a coat and leggings (and perhaps a separate skirt) of leather covered with overlapping pieces of metal, much like the scales of a fish. The suit includes gauntlets.
Plate. Plate consists of shaped, interlocking metal plates to cover the entire body. A suit of plate includes gauntlets, heavy leather boots, a visored helmet, and thick layers of padding underneath the armor. Buckles and straps distribute the weight over the body.