There are two overall regimes of light-matter coupling which offer different mechanisms for changing chemical reactivity: the weak coupling and the strong coupling regimes. The primary characteristic that differentiates these two regimes is whether the light-matter coupling strength g c is smaller than (weak coupling) or larger than (strong coupling) the various loss rates of the system. In the weak coupling regime, the primary mechanism for modifying chemistry is through an enhancement of the overall loss rate of the system, known as the Purcell effect. In this regime, there is a limited modification of the potential energy surfaces which limits the amount of control one has over modifying chemical reactions. On the other hand, in the strong coupling regime, significant changes to the potential energy surfaces can be observed and are adjustable based on fundamental physical characteristics such as the cavity frequency ω c and the light-matter coupling strength g c . These potential energy surface modifications, along with other factors such as the initial photonic state, the rate of cavity loss, and the presence of the dark state manifold, offer several mechanisms for theorists and experimentalists to use to control chemical reactivity in the strong coupling regime.