I don't have experience of that, but I have cold-cast using a resin and metal powder mix.
The results can be great as long as you get the measurements and ratios right, but it is quite costly as the good quality metal powders do not come cheap.
Al
Edit: Just to clarify, I'm talking about traditional cold casting which is approximately 40% resin and 60% metal powder.
There is another, less expensive way which I haven't tried - you coat the top layer of the mold with metal powder and add the resin inside as a filler. It'd be cheaper this way.
However, I like the traditional method as it looks and (due to the weight) feels like metal.