This study provides an in depth review of understanding the metabolic regulation of immune cells in cancer. Evidence has accumulated in the rapidly developing field of immune metabolism, in which immune cell function and fate are closely linked to their cellular metabolic programs, particularly within the tumor microenvironment. The TME is a metabolically disadvantaged niche characterized by hypoxia, nutrient deprivation, acidosis, and accumulation of immunosuppressive metabolites, all of which result from intense competition for essential resources such as glucose and amino acids. These metabolic constraints profoundly affect the activation, differentiation, and response capacity of the immune cells. This article systematically explores the metabolic reprogramming of immune cells in cancer, with a particular focus on T lymphocytes and myeloid cell populations. We have mapped the metabolic dynamics of T-cells from activation to dysfunction and depletion, elucidating myeloid lineage cells. Finally, we discuss emerging therapeutic strategies that target immune metabolism, including enhancing metabolic adaptation of effector cells, de-inhibiting metabolic checkpoints, reprogramming immunosuppressive cell populations, and combining metabolic interventions with existing immune checkpoint blockade therapies. A deeper understanding of metabolic competition and cooperation within the TME will provide conceptual and transformational evidence for developing more effective and durable cancer immunotherapy. Despite the promise of immunometabolic interventions, translating these strategies into safe and effective clinical therapies remains challenging.