It doesn't have to be a conventional metal, it could be that this metal has a very high boiling point, and that could be why it's not so hot. I'm not sure if I agree with this theory, but since all the magic systems we know of so far seem to be based on metal, and Vin says she burned the mist like metal, it was just a hypothesis. I just reread the part in WoA, and yes, it does say for sure that the Kandra and Koloss were created by the lord ruler, sorry about that. Anyway, if we do go with this metal mist hypothesis, then could we assume it's an alloy tothe metal in the lake near the original position of the well of ascension or the metal elend ate (which could be the same metal). I'm not sure I even believe the mist theory it's just a hypothesis. It might make sense though. One metal gives a person allomancy, the other strengthens it, they would be the same pair. I know most of the pairings do opposite things, but some of them do the similiar. For example: duralumin and aluminum both take metals away, they jsut do it in different ways, so they're not really exact opposites. Anyway, remember, all of this is purely theoreticalm I actually think the mists are probably water vapour of some supernatural nature like the characters in the book believe, but this is just something that came to mind.