Why is microwave heating so efficient and how can it be applied to metal melting and casting? A simple two-dimensional steady state thermal model of microwave heating will quickly teach you the thermal advantages of microwave heating and some of the parametric tradeoffs. This model provides the insight for thermal balance. The author will also briefly discuss the variations from steady state of the temporal model and the model versus design approximations. Often, in the microwave heating of ceramics, complex computer models are used to design the furnace and insulation. By avoiding certain materials and situations, microwaves are appropriate for heating metals or holding melts from small to medium size loads (as much as 1-5 tons). Some scaling issues are readily addressable by the simple thermal model. One aspect of the new paradigm for microwave melting of metals is the heating efficiency. Comparisons with inductive, resistive, and combustion furnaces will illustrate the differences with microwave furnaces.