 This paper provides an overview of the current research into defect engineered metal-based photocatalysts for water splitting. It discusses how defects can be used to control the optical absorption, charge separation and migration, and surface reactions, as well as their impact on the overall efficiency of the catalyst. Additionally, it examines the characterization techniques and DFT calculations used to understand the defect structure and its effects on the catalyst's performance. Finally, it highlights the challenges associated with developing more efficient and cost-effective defect engineered metal-based photocatalysts. This article was authored by Yong Chaoshan, Misha Afzal, Luan Pan, and others.