Under the sub-wavelength condition ($w<lambda/2$), an analytical model of light transmission and reflection through $1$D metallo-dielectric gratings of real metals has been developed. It has been shown that the transmission intensity associated with
the Fabry-Perot (FP) resonance of a $1$D metallo-dielectric grating of a real metal decreases with the increasing grating thickness and the dielectric constant of the ridge material. Further, it has also been demonstrated that the intensity of the FP resonance increases with the increasing slit width while it is independent of the grating period ($P$) and the incidence angle (when $P << lambda$
