This idea had crossed my mind also. But I had my doubts about it working, I thought the metal content would be too high. Looking at the article linked by jkopel, that appears to be correct.
However the testing described was performed in 2005, apparently. There have been new formulations of metal clay since then, maybe that would make a difference. There’s a new formulation of silver metal clay being produced in the US under the name MetalMagic that is 25% binder instead of the ~10-12% in other formulations. That may make a difference. Also there are the flex clays, which don’t dry completely. I believe most of those contain glycerin. This might also make a difference.
I don’t have any of the MetalMagic clay at the moment, but I do have some PMC Flex. I plan to do some testing once… Well, we all know how that sentence ends.