Radiotherapy (RT) plays a crucial role in tumor treatment and is an indispensable therapeutic approach. However, ionizing radiation often damages the normal tissues surrounding the tumor. Therefore, there is an urgent need for effective methods to improve the precision of RT. Nanotechnology has shown potential in enhancing the efficacy and safety of tumor RT. With the continuous development of multifunctional nanomaterials, various nanomaterials have been designed and investigated as radiation enhancers. Metallic nanomaterials are considered as promising radiosensitizers with potential for clinical translation. High atomic number (high‐Z) metal nanoparticles (NPs), such as gold and bismuth, have garnered increasing attention for their ability to enhance the radiation effect, as they can potentially improve RT outcomes. New nanomedicine strategies may help to advance RT. This paper concisely explains the radiation enhancement mechanisms of high‐Z metal NPs. It also enumerates several commonly studied high‐Z metallic nanomaterials used in tumor RT and discusses their potential clinical applications.