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This review article is involved in the metropolis theory debate. It analyzes actions aiming at creating, developing or managing entities identified by stakeholders as a metropolis. The focus is on metropolitan action objects, also on actors and their cooperation, and the devices maintaining the system homeostasis (regulation).Numerous and non-homogeneous actors co-operate in unstable and increasingly numerous games. They produce composite objects. Homeostasis is based on benchmarking, external constraints and the mobilizing ability of ""inventors of metropolis"".This highlights a paradox of the metropolis: it is strong due to the concentration of opportunities and resources and capacity development; it is weak because its equilibrium must be constantly rebuilt and because it is strongly dependent on the external constraints. The challenge is to bring together a large number of stakeholders around a narrative or a common project.