Melting is a physical process that results in the phase transition of a solid to a liquid. This process occurs when the internal energy of the solid increases, typically by the application of heat or pressure, which increases the substance's temperature to its melting point. At the melting point, the solid's lattice structure breaks down, and its particles become free to move past one another.

The melting point of a substance is the temperature at which it changes from a solid to a liquid at a given pressure. The melting point of a substance is a characteristic property that depends on its chemical composition and crystal structure.

The process of melting can be described in terms of the kinetic theory of matter. In a solid, the particles are held together by strong intermolecular forces and are arranged in a regular, ordered pattern. As the temperature of the solid increases, the particles gain more kinetic energy and begin to vibrate more vigorously. At the melting point, the particles have enough energy to overcome the intermolecular forces holding them in place, and they break free from their fixed positions. This results in the formation of a liquid, in which the particles are no longer arranged in a regular pattern and are free to move past one another.

Melting is an important process in many natural and industrial processes. For example, the melting of ice is responsible for the formation of rivers, lakes, and glaciers. The melting of metals is used in a variety of manufacturing processes, such as casting and forging.