In Chemistry, Entropy means the state of disorder, the randomness of the molecules.
Entropy does not affect melting point. But rather entropy can be compared base on the state of the substance.
For example the liquid form of water has higher entropy(disorder) than the solid water. A explanation that will give you credit in AP Chemistry is that ice molecules are locked in place as a solid, it has little space to move, where as water molecules are free flowing. So water molecules have greater entropy than ice molecules