Recent years have seen a dramatic expansion in ideas regarding the nature of dark matter, extending beyond the WIMP paradigm. Many of these theories predict minuscule couplings between light (sub-GeV mass) dark matter and the Standard Model, which direct detection experiments can search for. In this talk we will begin by reviewing the status of current electron-based experiments which are achieving extraordinary sensitivity to theoretically well-motivated freeze-in dark matter models. Next, we discuss how condensed matter sum rules can inform future detector development, and show how non-relativistic effective field theories can be used to understand the detector response to general dark matter-electron interactions. Finally, we will discuss how the next generation of direct detection experiments using meV-scale excitations, such as phonons and magnons, can begin to probe the sub-MeV dark matter mass frontier.