Abstract: Plasmonic nanocavities, owing to their unique capability to confine optical field within nanoscale, have emerged as a platform for overcoming the optical diffraction limit and enhancing light-matter interaction. This review presents recent advances in light-field regulation within nanocavities. We first introduce the plasmonic properties and spectral enhancement capabilities of both static and dynamic nanocavities. Subsequently, two types of active modulation approaches are discussed. The first involves introducing dynamic tunability via external fields to achieve control of resonance wavelength and field distribution. The second employs polarization engineering of incident light to selectively excite nanocavity-plasmonic modes, enabling the visualization of molecular multipole transitions. On this basis, we summarize research progress in application exploration such as ultrasensitive Raman examination, strong coupling, nonlinear optical enhancement, and nanoscale photocatalysis.