Over the past decade metallic nanoparticles (NPs) have been intensively studied due to their distinctive chemical and physical properties. With the continuous rise in antibiotic-resistant bacteria, it became necessary to search for and develop antibacterial agents capable of effectively destroying bacteria with limited side effects. The antibacterial properties of metal oxide nanoparticles such as TiO2 and ZnO open up the wide application of such agents in a huge range of industries including but not limited to food packaging, food equipment manufacturing, and food formulation. Whilst their toxicity to humans is not yet well established, the mechanisms of action by which these metal nanoparticles disrupt bacterial cells are important to understand.