Myxococcus xanthus is a predatory bacterium and a model system for social behaviour in bacteria. Myx. xanthus forms thin biofilms, where cells work together to colonize new territory, invade prey colonies and lyse prey cells. Prey-cell lysis occurs at close proximity, and utilizes antibiotics such as myxovirescin, hydrolytic enzymes such as the protease MepA and extracellular outer-membrane vesicles that may facilitate delivery. Many questions about the mechanism of prey lysis remain, as well as a complete understanding of the vast hydrolytic and secondary metabolite potential present in the Myx. xanthus genome. However, it is clear that predation presents unique challenges for this bacterium, which are solved, in part, through the social behaviours at the disposal of Myx. xanthus. Here, we discuss the life cycle of Myx. xanthus, and the hypothesis that multicellular behaviour in this organism is critical to, and derives from, the challenges of growth as a bacterial predator.