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.
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?
Fuel Gas & Melting Temperatures - Different fuel gasses (acetylene, propane, natural gas) burn at different temperatures and are best suited for different jewelry operations. This chart outlines the maximum temperatures at which common fuel gasses burn along with the melting points of some of the most common metals used in jewelry and metalsmithing.