Metals Melting Temperatures Chart - but I'm not 100% about this one. It lists sterling as melting at a lower temp than fine silver and I thought you fused with fine silver because of its lower melting temp.... more research is needed?
Gallium || Ga
This element is so interesting. It has a melting temperature of about 85 degrees Fahrenheit, which is basically room temperature. If you hold this metal it will begin to melt in your hand.