Thermites have been used for over a century for joining applications and in this paper we present fully dense diluted thermite foils that react in a self-propagating manner and produce sufficient heat and molten braze to join aluminum-, magnesium-, and iron-based alloys. Al:NiO, Al:CuO, and Al:Cu2O thermite systems were systematically diluted with Ni or Cu to decrease the maximum reaction temperature and hence the amount of gas generated during the self-propagating reactions. Velocities and mass ejection were measured for reactions within free-standing foils as a function of dilution. The dilution that leads to quenching during propagation within a bond is identified, and finally, Al:NiO:10wt%Ni and Al:CuO:40wt%Cu foils were used to demonstrate the ability to join aluminum-, magnesium-, and iron-based alloys.