This Thesis presents a study of the nature of the different stages of galaxy mergers that lead to the formation of massive galaxies. In particular we look into the properties of infrared bright mergers, spheroidal post-mergers and star-forming early-types and how their properties compare and contrast with the properties of regular late and early-type galaxies. The aim of this thesis is to expand our knowledge of the merging process and to find a justification for the variability of the more active early-type galaxies. These studies were performed by extracting all the possible information from different surveys. For the optical analysis we used the Sloan Digital Sky Survey (SDSS), while we used surveys conducted by IRAS and GALEX for infrared and ultraviolet data respectively. To better understand the mergers/massive galaxies connection we performed the first detailed analysis of spheroidal post-mergers, as well as the first infrared- blind study of the properties of merging galaxies and produced a multi-wavelength catalogue of local star-forming early-type galaxies. We also looked at the more general galaxy population by constructing the largest morphological survey of far- infrared selected objects, which provided us with the first estimate of how different morphologies (but mergers in particular) contribute to the local SF budget. The results show the pivotal role played by mergers in the formation of stars and evolution of galaxies in the local Universe.