My understanding is they take the natural oil of palm, corn and so forth and force hydrogen gas into it at very high pressure to cause a catalytic affect. They do this to preserve the oil because natural oil turns rancid quickly. Actually, that is the key to know what is healthy or not because usually healthy foods spoil quickly in their natural state where as unhealthy food have been chemically altered to last long on super market shelves. The 'metal' is an actual metal such as nickel, platinum or even aluminum that alters the molecular state of the natural oil to one that can last for a long time or in other words - plastic. You are literally eating plastic when you eat hydrogenated oil - what's worst is it is very hard for the body to get rid of it because of its artificial structure.