Several factors can affect melting point as follow
Composition of molecules
The melting point is higher for a substance in which the molecules are tightly packed compared to a substance in which the molecules are far apart from each other
Pressure:
The greater the pressure applied to a substance, the lower its melting point.
Impurities:
Solids containing impurities melt at low temperatures
Particle shape and size:
A substance has a higher melting point when the molecules are tightly bound together and when the spaces between them are small.