The substitution of aluminum for steel could be limited or reversed by green steel subsidies or the rise of other light metals. Sustained subsidies that promote green steel or green hydrogen, but not low-carbon aluminum, could hold back a metal transition. Compared to aluminum, magnesium has an even higher strength-to-weight ratio, requires even more energy to produce, and is, at present, even higher cost. Titanium and carbon fiber are more expensive still, and by many metrics more functional. The same trends of electrification and dematerialization that point toward aluminum use at the expense of steel may lead to the cannibalization of aluminum demand by other light metals.