While this might be a bit too technical for anything that would actually be written in Bionicle canon, Magnetism could allow generation of an electric field in the right circumstances.
A proper degree of control over a magnetic field would allow a Toa of Magnetism to heat up metal extremely quickly through induction. A Toa of Iron may also be able to heat (and cool) metal if he had atomic-level control over the metal, but that seems less likely.
Also, Magnetism could plausibly allow for a similar degree of metal manipulation as a Toa of Iron, though Greg has said otherwise in the past:
As for a more general idea, I’ve thought before that Toa of Magnetism, Lightning, and Iron would be a ridiculous team, and could form a very synergetic kaita.