Metropolises represent the latest and most sophisticated form of human settlement, while metropolitanization is occurring faster than global population growth. Despite the absence of a unified theoretical framework for defining housing unaffordability, this crisis is widely recognized as one of the greatest challenges in today's metropolises. Systematic analysis shows the lack of a multi-level understanding of the phenomenon. The study concludes by emphasizing the imperative for institutional reforms in urban governance to identify and implement appropriate policy solutions. Systematic review and critical realism describe the events and consequences of housing unaffordability at the level of objective reality. Identified outcomes include increased poverty, spatial segregation, informal settlements, diminished quality of life, and environmental threats. The underlying structures and causal relationships of this phenomenon were analyzed within a systematic dataset, revealing five key dimensions: governance and housing policy structures, economic structures, spatial and urban infrastructure systems, socio-cultural structures, and urban sustainability frameworks. Using retroductive logic, the research interprets findings across multiple layers of reality, examining the relationship between the generative mechanisms of housing unaffordability and metropolitanization. Through explanatory inference, the study redefines the theoretical foundations supporting housing affordability and presents two validated hypotheses. Findings demonstrate that observed consequences emerge through the financialization of housing and policy misalignment between local governments and key institutional actors. The results indicate that metropolitanization intensifies these mechanisms by exacerbating resource competition, increasing land values, and complicating urban governance