Chemical reactions under the influence of light play a paramount role in everyday life, from fundamental biological mechanisms to sustainable energy applications. Therefore, controlling and optimizing the underlying chemical processes is of great interest.

The use of (oriented) classical electric fields to modify chemical reactions is a promising, emerging technique. In this talk, I will discuss a non-empirical linear free energy relationship that microscopically relates field-induced changes in the activation energy to those in the reaction energy, providing a powerful new framework for design and characterization of electrostatic catalysis. On the other hand, experimental developments in the emerging field of polaritonic chemistry opened up new possibilities of modifying and controlling chemical processes that depend on the interaction of quantized light fields with matter. I will give an overview of strong light-matter interaction that arises when matter is confined in optical cavities, its computational challenges and potential solutions focusing on mixed quantum-classical methods for photons.