In a cold dark matter universe, galaxy interactions and mergers are a ubiquitous and inescapable aspect of galaxy evolution. By violently relaxing stars and channeling gas into nuclear starbursts, these interactions may explain a host of phenomena, including the fueling of bright quasars and buildup of the most massive black hole populations, the formation of the bulk of the elliptical/spheroid population, and the existence of tight correlations between the two. The amount of gas in galaxies is critical for their black hole fueling and the structural properties of the remnant, and can even allow major mergers to produce disk-dominated remnants. I’ll give an overview of recent modeling of these phenomena, and show how they can provide a solution for some of the supposed problems of the cold dark matter model while also providing new empirical ways to investigate the histories of today’s galaxies. I’ll also discuss how models of black hole growth with feedback from an actively accreting AGN may be a critical component of this resolution, and how such models have changed our understanding of when and how black holes and spheroids grow.