Background: Metabolic syndrome (MetS), characterized by central obesity, insulin resistance, dyslipidemia, and hypertension, has emerged as a major global health challenge. While traditionally associated with diabetes and cardiovascular disease, MetS is increasingly recognized as a precursor to several malignancies. Objective: This review synthesizes epidemiological evidence and mechanistic insights linking MetS to carcinogenesis and highlights the implications for internal medicine practice. Methods: Literature was reviewed from PubMed, Scopus, and Web of Science (2000–2025) using the terms “metabolic syndrome,” “carcinogenesis,” “internal medicine,” and “cancer risk.” Priority was given to meta-analyses, large cohort studies, and mechanistic research. Results: MetS was associated with a higher incidence of colorectal, breast, hepatocellular, pancreatic, endometrial, and other cancers. The mechanistic pathways include insulin resistance and IGF-1 signaling, chronic inflammation, adipokine imbalance, oxidative stress, NAFLD/MASH progression, microbiome alterations, and hypoxia-driven angiogenesis. Preventive strategies, such as lifestyle modifications, weight loss, targeted screening, and selected pharmacological interventions (e.g., metformin, statins, GLP-1 receptor agonists, and aspirin), are promising.