Solder used for electronics is a metal alloy, made by combining tin and lead in different proportions. You can usually find these proportions marked on the various types of solder available.
With most tin/lead solder combinations, melting does not take place all at once. Fifty-fifty solder begins to melt at 183 C -361 F, but it's not fully melted until the temperature reaches 216 C - 420 F. Between these two temperatures, the solder exists in a plastic or semi-liquid state.
the properties of gallium makes it to be liquid at room temperature
Elemental gallium is a soft, silvery blue metal at standard temperature and pressure, a brittle solid at low temperatures, and a liquid at temperatures greater than 29.76 °C (85.57 °F) (above room temperature, but below the normal human body temperature)
the properties vary beacuse of their difference in melting points