High volumetric, steady state flow rates of metal compositions can be rapidly melted, or otherwise heated to a desired degree, by conveying the metal composition (106) through the length of a microwave chamber (140) containing a microwave susceptor (150) in thermal contact with the flow. Microwave energy is propagated in the cavity to heat the microwave susceptor. The resultant thermal energy is then transferred to the metal composition. Because metal compositions tend to be excellent heat conductors, the transfer of thermal energy from the susceptor throughout the volume of the metal composition occurs quickly. Indeed, enough thermal energy can be generated to easily melt nonferrous metal alloys in connection with steady state die casting operations. Microwave melting would occur so rapidly, that significant reductions in cycle time would be achieved. Additionally, the use of microwave energy for melting is economically advantageous, because microwave heating is extremely energy efficient.