Monoclonal gammopathy of undetermined significance (MGUS) and smoldering multiple myeloma (SMM) are premalignant stages in the development of multiple myeloma (MM). Advances in detection, risk stratification, and therapeutic intervention have transformed our understanding of disease progression. Sensitive techniques like mass spectrometry have identified smaller monoclonal gammopathies, such as monoclonal gammopathy of indeterminate potential (MGIP), which may precede MGUS. Risk stratification models for MGUS and SMM, including the Mayo Clinic, PETHEMA, 2/20/20, IMWG, and PANGEA models, leverage tumor burden markers and cytogenetic abnormalities to predict prognosis. Genomic studies have revealed mutations, structural changes, and mutational signatures that predict progression. Immune microenvironmental alterations underscore the multifactorial nature of disease evolution, while epigenetics is emerging as a source of tumoral and microenvironmental changes. Therapies for high-risk SMM, including lenalidomide, daratumumab, and next-generation immunotherapies, demonstrate efficacy in delaying progression to MM but raise concerns regarding safety in asymptomatic patients. Future research must refine prognostic models, integrate genomic and immunophenotypic data, and establish consensus on optimal strategies for early intervention. This comprehensive review highlights the biological, clinical, and therapeutic advancements in MM and its precursors, emphasizing the importance of early risk assessment and targeted treatment to improve outcomes.