Transmission of heat is the process by which energy is transferred from one object to another. Conduction is one of the three main methods of heat transfer, along with convection and radiation. In conduction, heat is transferred through direct contact between two objects, such as when a metal spoon is placed in a hot liquid. The molecules of the spoon become excited and vibrate, transferring their energy to the liquid. This process continues until the two objects reach thermal equilibrium.