The distribution of stellar metallicities within and across galaxies is an excellent relic of the chemical evolution across cosmic time. Spatially resolved spectroscopic surveys offer the unique opportunity to study global and local drivers of stellar populations in galaxies. In this talk, I present results from a detailed analysis of spatially resolved stellar populations based on > 2.6 million spatial bins from 8109 nearby galaxies in the SDSS-IV MaNGA survey. Our study goes beyond the well-known global mass-metallicity relation and radial metallicity gradients by providing a statistically sound exploration of local relations between stellar metallicity, stellar surface mass density (SMD) and galactocentric distance in the global mass-morphology plane. We find a significant resolved SMD-metallicity relation for galaxies of all types and masses. The spread of the relation is mainly attributed to different radial distances. In particular, we find that at fixed SMD metallicity increases with radius. This result calls for a driver of metallicity in addition to SMD that promotes chemical enrichments in the outer parts of galaxies more strongly than in the inner parts.