Photonic materials, including plasmons and polaritons, are highly promising catalysts for driving energetically unfavorable chemical reactions with sunlight, due to their large optical cross sections and ability to modify potential energy landscapes. However, the efficiencies of most plasmon-driven and polariton-driven processes are quite low, likely due to the lack of mechanistic understanding of the underlying physical processes. Here I’ll discuss our use of Raman spectroscopies to advance our fundamental understanding of these systems. First, I’ll describe our development of ultrafast surface-enhanced Raman spectroscopy (SERS) to probe the contributions of plasmon-generated hot electron transfer, heating, and vibrational energy transfer on timescales relevant to photocatalysis. Second, I will talk about our efforts in mapping out reaction coordinates in polaritonic systems, quantifying the degree of mode-specific activation. These efforts in developing a fundamental understanding of polariton and plasmon-mediated processes in molecules will ultimately aid in the rational design of cost-effective photonic materials capable of driving industrially relevant chemistries using solar radiation.