The function of the immune system is essential for defending the body against infections and diseases and maintaining overall homeostasis. Metabolism, the set of life-sustaining chemical reactions within cells plays a crucial role in supporting immune responses. In immune cells, metabolic reprogramming is essential for meeting the energetic and biosynthetic demands required for effective immune responses. Various aspects affect the metabolic reprogramming of immune cells and its significance in immune activation and regulation. This chapter delves into the intricate relationship between metabolism and immunity, highlighting how metabolic pathways influence the activation, differentiation, and function of immune cells. By understanding these connections, we can gain insights into potential therapeutic strategies for modulating immune responses in various diseases.