A hybrid metal-dielectric photonic crystal, a thin opal slab coated by a gold film, has been designed in order to exercise additional control upon the light propagation in a photonic band-gap material using extraordinary optical transmission in the corrugated gold film. The photonic and plasmonic components of the hybrid crystal are closely linked, because the photonic crystal lattice provides a spatial template for the gold film corrugation and modifies the electromagnetic vacuum in the vicinity of the gold film. Due to coupling of light diffracted in the opal lattice to surface plasmon polaritons in the metal film, the spectra and angle diagrams of transmission in hybrid structures deviate from the linear superposition of transmission functions of both hybrid components. In particular, the selective conversion of diffraction minima, and cavity mode and thickness dependence of the surface plasmon polariton-related properties have been observed. The synergy of three resonance mechanisms behind the functionality of hybrid photonic crystals provides a uniquely broad tunability of their optical properties.