Metropolis is also the metropolitan section of the United Cities & Local Government organization (UCLG), which arose from the merger between the IULA and UTO. Its mission is to promote international cooperation and exchanges among members, i.e., local and metropolitan governments. Metropolis is the spokesperson on cities' interests in international forums.

The metropolises are shaping the 21 st century. While individually different, they share modern-day concerns on issues such as urban planning and development, the economy, health, environmental matters, transport, infrastructure and communications.

Created in 1985, the Metropolis Association is represented by more than 90 member cities from across the world and operates as an international forum for exploring issues and concerns common to all big cities.

The main goal of the association is to better control the development process of metropolitan areas in order to enhance the wellbeing of their citizens. To do this, Metropolis represents regions and metropolitan areas at the worldwide level and is recognized as a major player by large international organizations such as the UN, WHO, the World Bank and others.