Composite metal filaments are a mix of metal powder and either PLA or ABS. The resultant filament can produce results that have the look and feel of metal objects, including the weight, as the blended mixture tends to be several times denser than pure PLA or ABS.
Some of the available metal blends include brass, bronze, copper, steel etc. Ideal applications will be miniatures, mementos, artifacts, figurines, toys etc. Also, these objects allow post processing like polishing, weathering or tarnishing a bit to get the required look and finish.