Melting
Ice is the solid crystalline form of water. In a crystalline solid the molecules (or ions) are bound together in a regular repeating pattern. When ice is heated, its molecules vibrate faster and faster until the bonds are broken and the crystalline solid becomes a liquid. Minerals are crystalline solids, just like ice, and so they melt in the same way. But rocks usually consist of more than one type of mineral, each of which has its own distinct melting point. So rock melts in successive steps as it is heated beyond the melting point of each of its minerals.
*Partial Melting: Often the preexisting rock melts only partially, creating magma consisting of the minerals with low melting points and leaving behind a rock made up of minerals with high melting temperatures. Other factors also control the melting of rock. The more water included in the rock, either in pore spaces or in the mineral structure, the lower the melting point (temperature at which the rock melts). This is one reason that volcanoes are typically found near subduction zones. Subducting oceanic crust carries water downward with it, down below the hot dry lithosphere of the overriding plate. The water then rises into the upper plate and lowers the melting temperature of the lithosphere rocks, creating magma from partial melting.