Evolution of galaxies through cosmic time is closely governed by gas flow processes occurring within and around them. Accretion of gas, which fuels star formation, and outflows, which replenish the surrounding regions with baryons, take place in the galactic haloes. Beyond the galactic haloes, the environment plays a fundamental role in shaping the way galaxies evolve. In the local Universe, mergers and interactions have been observed to affect the distribution and physical conditions of gas around galaxies. Further, these interactions are predicted to funnel large quantities of gas to the central regions of galaxies, triggering intense bursts of star formation and fueling Active Galactic Nuclei (AGNs). Feedback from the AGN and star formation activity can have a strong impact on the evolution of the host galaxies and their environment. However, we currently lack robust observational constraints on several aspects of the above picture of galaxy evolution. For example, how do galaxy mergers affect the distribution of gas within galaxies? How does the environment influence the distribution of gas and metals around galaxies? How are the properties of gas connected with AGN and star formation activity? To shed light on these questions, we have conducted multi-wavelength observational studies of gas and galaxies including studies of atomic hydrogen gas in centres of galaxy mergers and studies of metal-enriched halo gas across galaxy overdensities. This talk will present the key results from these studies and discuss briefly the prospects of taking such studies forward with existing and upcoming observational facilities.