A Toa of Magnetism could only affect metallic protodermis, no other forms of protodermis.
Not all metals were magnetic.
Toa-level control over magnetism would allow a being to warp and shape the physical structure of metals.
Toa level control over magnetism would allow a being to lift, throw around, pull apart, twist, shape, or crush other beings.
A Toa of Magnetism could affect metal.
Though Jovan had gunmetal gray, black, and blue parts, these were not necessarily the primary colors of Magnetism and other colors might be present on beings of that element.