Working with metal clay is much different than traditional metalsmithing. When it is in its green state, metal clay is worked like ceramic or polymer clay. You can mold it, stamp it, cut it with a butter knife.
When it dries before firing, you can use tools like emery boards and sandpaper to finish it, and smooth it.
However, once you fire metal clay, you have a piece of metal to work with. It is at this point that you can use metalsmithing techniques like soldering, sawing, and drilling.
The original versions of metal clay were made by mistake, as a by product of another manufacturing process. The clay is made up of particles of the precious metal, combined with a non-toxic, organic binder. This binder burns away when the metal clay is fired, leaving only the metal behind that becomes fused together in the firing process.
Firing can be done in a household, even if you use a metal clay kiln. The kilns are tabletop kilns that can plug into a standard outlet. Other methods of firing are available for smaller pieces if you use the low temperature versions of the metal clay. Not all metal clays are available in low temperature versions.
Although originally metal clay was only available in silver and gold, in the last couple of years, a new copper and bronze clay has been manufactured. So now the clay itself is much less costly.