The metal dice I've seen have been smaller than most plastic dice are, I assume to reduce costs as well as weight because who wants to be rolling around a half pound of dice in their hand as well as see the family fine-furniture dining table get covered with little triangular marks from the corners of repeatedly falling heavy bits of metal?
Now, precision-milled plastic dice, or maybe resin or something like that. That'd be something I'd be more interested in. Hmn... thinking about it just now I think aircraft-grade aluminum might be a choice for dice. Still get scuffed and scratched but I think I could own a set. I've thought a few times about maybe getting some of those 3D-printed dice, but haven't found a set that looks USABLE while still looking cool enough to want to own.
Thing is, though, it'd be just for fun - just to be geeky. For all the touting of the accuracy and precision of Gamescience dice (for example) the effect on probabilities in RPG's is insignificant. What I won't tolerate is dice made of cheap, low-impact, brittle plastic. The kind described whose edges and corners wear away until it's almost more of a ball than a faceted solid. I had a friend who ran a game using a pair of d20's made of that cheap stuff. He'd actually deliberately filed down the corners and edges - so much so you could see it from 10' away. One he filed down so it would always roll low and the other would always roll high. We eventually forbid him to use them for anything, ever, and I think even he realized he was being a bit of a wanker about it.
But playing D&D is not the same thing as rolling dice in a casino tens of thousands of times a day FOR MONEY. There a thousandth of a inch can mean hundreds and thousands of dollars of lost profit. In D&D the results of our die rolls are UTTERLY buried in the noise of the purpose of the roll and all of the variables being applied to our chances of success/failure. Precision dice are therefore simply unnecessary. Because of that the major sales points for dice seem to be their variety of colors and their readability rather than precision. I MIGHT buy a set if they seem cool or geeky enough but aren't outrageously priced.