Also, metals can easily accommodate varying number of electrons in the electron shells of their atoms and still be stable. That makes them very good to quickly store and release electrons which means they can help say transfer molecules around (iron for transport of gasses), scavenge free radicals (e.g. manganese) etc.
Do we have any theories as to why complex life eventually started requiring various metal elements as micronutrients?
For example, why did zinc, of all things, start getting utilized by brain and prostate tissue in humans?