The chemical composition of the gas and star formation rates (SFRs) in galaxies over cosmic time provide very important tools for understanding galaxy evolution. Although there are many studies at high redshift, they are rather scarce at lower redshifts. However, low redshift studies can provide important clues about the evolution of galaxies, furnishing the required link between the local and high redshift universe. With this purpose, we analyzed the metallicity, mass, luminosity, SFR, and morphology of star-forming galaxies from SDSS-DR5 in the redshifts range 0.04 < z < 0.4. We used data processed with the STARLIGHT spectral synthesis code, correcting the fluxes for dust extinction, and estimating metallicities using the R_23 method. SFRs were estimated by means of the Ha emission flux following Kennicutt et al. (1998), and morphology was determined by color, concentration index, and specific SFR diagrams. We analyze the evolution of the luminosity and mass-metallicity relations, as well as the evolution of the SFR and morphology. There is a clear evolution for galaxies at higher redshift (0.3 < z < 0.4), showing higher SFRs, lower metallicities, and late-type morphologies. By dividing our redshift samples in intervals of similar magnitude and comparing them, significant signs of metallicity evolution are found. Metallicity correlates inversely with redshift: from redshift 0 to 0.4 a decrement of 0.1 dex in 12+log(O/H) is found.