Both Iron and Copper are used to oxidize in certain body functions, but if a super-oxidizer already exists in the body tissue and blood then both these are altered or marked for excretion. From memory copper is required to change Iodide to a bio-available form of Iodine by the thyroid.
Iron is easier to grasp; we ingest iron then a super-oxidizer like Hg oxidizes it to rust and we become both iron (rust) toxic and iron deficient...