The technique of frequency-modulation enhanced magnetic rotation spectroscopy (FM-MRS) is applied here to the study of the electronic spectra of gas-phase transition metal hydrides and deuterides. Experimental FM-MR results for several bands of PdH, PdD, NiH, and CuH are presented. In the case of PdH, an Omega=0.5-X Omega=0.5 band at 4371 Angstrom has been observed and assigned. Prior to this work, although several bands of PdD had been reported previously, no electronic transitions of PdH had been assigned. All of the PdH, PdD, and NiH bands studied in the 4200-4600 Angstrom wavelength region are strongly predissociated, and in the case of PdH and PdD, strongly and multiply perturbed as well.