While the aforementioned photochemical experiments have demonstrated some promise for cavity-controlled photochemistry, recent theoretical investigations on the topic have shown a wider array of ways to control photochemistry with polaritons and have elucidated the possible mechanisms behind this control. The following section details some of these theoretical works in polariton photochemistry. Section 4.1 outlines various methods for performing non-adiabatic polariton photochemical simulations. Section 4.2 describes how light-matter hybridization allows for control over photochemical processes. Section 4.3 overviews the results of realistic ab initio simulations of cavity-coupled photo-isomerization reactions. Section 4.4 outlines the various ways that light-matter coupling can control charge transfer reactions. Section 4.5 details the influence of cavity-induced conical intersections on photochemical reactions. Section 4.6 introduces how the initial state of the photonic mode can be manipulated to influence photochemical dynamics. Lastly, Section 4.7 goes over the impact of cavity loss on photochemical reactivity.