In the Outline of 14th Five-Year Plan and the Long-Range Objectives through the Year 2035, the important task of "leveraging the driving role of central cities and urban agglomerations to build modern metropolitan areas" is clearly proposed, which is a key content for deepening the implementation of the new urbanization and regional coordinated development strategy. Metropolitan areas, characterized by their "core-periphery" structure, facilitate the free flow of resources, unleash market dynamism and social creativity, emerging as the key drivers of high-quality economic development and urban renewal. What repercussions will this yield on regional development? Are there discrepancies in its effects on cities with cross-boundary or diverse spatial attributes? What underlies these disparities? Furthermore, what experiential insights will the rich practical experience of the metropolitan areas in the Yangtze River Delta offer to the increasing number of cities embracing modern metropolitan paradigms? Addressing these queries will contribute to a deeper analysis of the current status and formation mechanisms of China’s urban agglomeration development, holding significant practical implications for theoretical research and policy formulation concerning urban economic development and regional economic integration. Firstly, this paper adopts a spatial econometric model to study the data from Statistical Yearbook of Chinese cities, analyzes the spatiotemporal evolution characteristics of urban economic development in the Yangtze River Delta, and focuses on the role of metropolitan area in regional economic development. This paper finds that compared to the entire Yangtze River Delta, urban economic development within the metropolitan area is more balanced, and there is a significant spillover effect in the economic development of the metropolitan area. Second, this paper constructs industry data at the city pair level based on the China Industrial Enterprise Database. In order to overcome endogeneity challenges, this paper uses the share shifting method to construct Bartik instrumental variables and identified the industry level spillover effects of the core city of the metropolitan area on the peripheral cities. Considering the impact of industrial correlation effects, the authors examine the role of industrial structure similarity among the cities and find that the higher the industrial structure similarity between the core city and peripheral cities, the stronger the spillover effect of the central city. At the same time, there are differences in the spillover effects obtained by peripheral cities affected by multiple growth poles and a single growth pole. Peripheral cities influenced by multiple growth poles attracted more labor, leading to stronger spillover effects. In addition, this paper also finds that spatial spillover of metropolitan area can break through administrative boundaries, which helps local governments coordinate and thereby enhance the spillover effect of core cities. To accelerate the development and growth of metropolitan areas, we should actively leverage the spillover effects driven by core cities and promote regional coordinated development through the integration of metropolitan areas. At the same time, we should support the integrated and collaborative development of multi-center, multi-level metropolitan areas, and deepen cooperation and division of labor within metropolitan areas. Furthermore, we need to innovate the mechanisms for sharing the benefits of metropolitan areas among cities, actively explore institutional and system innovations for metropolitan area integration, focus on breaking down the administrative barriers and eliminate invisible obstacles between administrative regions.