A theoretical model has been developed for molten metal/water interactions by using a semiempirical heat transfer correlation and a mass transfer analogy to predict the metal ignition threshold temperatures for aluminum and zirconium. The predictions of the aluminum and zirconium metal temperature responses are studied to identify self-propagating chemical reactions that lead to metal ignition for various metal particle sizes and initial temperatures. The results showed that the ignition of the aluminum metal is possible when the aluminum oxide layer remains in the liquid phase until the metal temperature reaches its oxide layer solidification temperature under highly transient conditions. For both metals, the ignition temperature increased with a larger size of the metal particle, with zirconium requiring qualitatively larger temperatures for ignitions. It was observed that the effect of the water temperature strongly depends on where the chemical reaction front may actually be located.