If the human condition can be medically described as an organic body, the metalface condition is best described as a cyberneural body. This term is based around the cyberneural heart which gives life to every metalface.
A cyberneural body is subject to extreme temperature changes as well as electrical damage and certain types of radiation. However, changes in air/water pressure, moisture or liquid, lack of air, or any kind of poison or lethal chemical are ineffective on the cyberneural body.
UPDATE: Certain types of acid (such as hydrochloric) are incredibly destructive to metalface if exposed to certain areas of the internal components. This is due to the cyberneural body's ability to slow acidic digestion combined with the inadvertent tenancy of acid to mix with circulatory liquids in the body which causes the acid to spread quickly to critical areas.