Metropolitan area is a contiguous urban agglomeration composed of a core city and its surrounding areas, and it is a region with close economic, social and spatial ties. The significance and function of metropolitan area are mainly reflected in the following aspects: 1. Economic development: Metropolitan area has gathered a large number of people, enterprises and resources, forming a good economic scale and market potential. Through industrial coordination and optimal allocation of resources, metropolitan area can provide more employment opportunities, attract more investment and innovation activities, and promote rapid economic development. 2. Regional coordination: Metropolitan area can coordinate the development between cities and reduce the competition and waste of resources between cities. By * * * sharing planning, cooperation and resources * * *, the metropolitan area can realize the complementarity and coordination among regions and promote the sustainable development of the whole region. 3. Urban function expansion: Metropolitan areas can realize the expansion and optimization of urban functions. Different cities can give full play to their respective advantages, form characteristic industries and services, provide diversified employment and life choices, and improve residents' quality of life and happiness. 4. Intensive utilization of resources: Metropolitan area can realize intensive utilization of resources and sustainable development of environment. Through cooperation and coordination among cities, metropolitan area can optimize land use, energy consumption and transportation, reduce environmental pollution and ecological damage, and realize effective and sustainable utilization of resources.