Radiotherapy, one of the most utilized strategies to combat malignancies, has been constantly explored for its effectiveness and optimized, and it is currently operating at the molecular level. The tumor microenvironment (TME), where complicated changes take place under radiotherapy and other treatments, inevitably draws our attention to metabolic alterations, immunogenic cell death (ICD) and immunological interactions. In response to radiotherapy, tumor metabolism promotes DNA and membrane repair processes and reduces oxidative stress, thereby collectively alleviating the occurrence of cell death. Moreover, the induction of pyroptosis, necroptosis and ferroptosis under radiotherapy has the potential to increase antitumor immunity. Therefore, comprehensive knowledge about how radiotherapy triggers these modalities of ICD mechanically is necessary for developing nanomedicines with more accurate targets. In addition, information on clinical advancements as well as the management of adverse events is important for investigating radiotherapy combined with immunotherapy. This review provides an overview of up-to-date findings on metabolic changes and ICD under radiotherapy and provides insight into the status of the TME.