We present a theoretical investigation on the pulsational behavior of metal-rich RR Lyrae variables over the range of evolutionary parameters suitable for stars with metallicities Z= 0.006 , 0.01 and 0.02 .
With the addition of similar results for metal-poor pulsators we discuss the theoretical pulsational scenario covering the metallicity range from Z=0.0001 to 0.02 .

By connecting pulsational constraints to evolutionary prescriptions for He burning stars we discuss the observed behavior of the RR Lyrae population in the Galactic field .
We find that the distribution of field ab -type RR Lyrae stars in the period-metallicity plane can be easily understood within the framework of the present theoretical scenario , suggesting that the Oosterhoff dichotomy also affects field variables .

Theoretical predictions concerning the amplitude-period diagram are discussed and compared with observational data .
We find a general agreement for metal-poor ( [ Fe/H ] < -1.4 ) RR Lyrae stars , whereas more metal-rich variables show amplitudes smaller than those predicted for pulsators originated from old , low-mass evolving stars .
Alternatively , the agreement between theory and observations would require that a substantial fraction of metal-rich RR Lyrae variables in the Galactic field were younger than \approx 2 Gyr .

The comparison between the pulsational behavior of RR Lyrae either in the Galactic field or in the Galactic bulge discloses the evidence that , at least as far as RR Lyrae variables are concerned , the metal-rich components of the bulge and of the field population appear quite similar .
We finally suggest that the peak at log P \simeq -0.55 in the period frequency distribution of first overtone RR Lyrae stars in the Large Magellanic Cloud , considered as possible evidence for second overtone pulsators , could be more simply taken as evidence of a metal-rich stellar population .