We investigate the coupling properties between plasmonic modes and cavity modes in corrugated metal–dielectric–metal structures. According to the symmetric property of mode field distributions, strong coupling and non-coupling behaviors exist between the cavity modes and plasmonic modes, referring to the short-range, long-range and gap plasmon polaritons modes. Correspondingly, the crossing and anti-crossing behaviors of the dispersion relations appear in the reflection spectra by varying thickness of middle layer dielectric. It is found that the cavity length strongly impacts the mode distribution and the coupling properties. The coupling behavior was discussed using the coupled oscillator model, and our theoretical results are in good agreement with the numerical ones.