Abstract: I will describe how Gravitational Waves alter the dynamics of cavities, focusing on electromagnetic Superconducting Radio-Frequency cavities. I will mostly describe the way in which the passage of gravitational waves generates mode mixing by either their effect on the electromagnetic field or by interacting with the boundaries of the cavity. For completeness, I'll also mention the way gravitational waves interact with systems of spin. I shall finish with rough estimates of sensitivities for some current detectors.