Metal-doped ZnO nanoparticles were prepared using the co-precipitation synthesis method to analyze their optical and structural properties. Five different samples with the formula A_XZn_1-XO (where A = Ni, Cu, Co, Cd, Sr, and X = 0.01) were prepared by using the same doping concentration. X-ray diffraction (XRD) measurement confirmed that all prepared samples maintained a single-phase structure without having any secondary oxide peaks. Fourier-transform infrared (FTIR) spectroscopy showed the presence of functional groups such as carboxylate, zinc carboxylate, and hydroxide. The surface morphology of the samples was examined using scanning electron microscopy (SEM), which revealed the formation of both nanoparticles and nanorods. The particle sizes were approximately in the range of 50 nm and varied depending on the dopant used. The optical properties, particularly the electronic and optical band gaps, were analyzed using UV-Visible absorption spectroscopy and Tauc plots. It was calculated that the band gap increased from 3.37 eV in pure ZnO to about ~3.8 eV in the doped samples, depending on the dopant. These results suggest that the type of metal dopant has a significant impact on the optical behavior of ZnO. The doped ZnO nanoparticles demonstrate promising potential for use in various applications, including transparent electronics, UV LEDs and lasers, UV-blocking coatings, photocatalysis, and consumer products such as sunblock and sunglasses.