The French territorial system is marked by a historical very large communal dispersion. Strangely the French State, although considered very strong, has never managed to impose the merger of these municipalities, as was the case in most other European countries. This resistance of local elected representatives, often also national parliamentarians, then led the central government to use another strategy: their grouping in public institutions of intermunicipal cooperation (EPCI). The creation of the Metropolis of Lyon is, therefore, very original. Created by the law of 27th January, 2014, it is the only “metropolis” with the status of territorial collectivity and merges on its territory the Rhône department and the former “urban community” of Lyon. This metropolis is thus unique in France, and the authors will tend to verify whether it could serve as a model to follow by other metropolises, considering the case of the first institutionalised metropolis in Poland, namely the GZM Metropolis, which is struggling with structural problems. The GZM Metropolis was established in 2017 by the Polish Parliament’s law and provided with a specific governance regime comparable to the “manager and council model” and decision-making based on a double majority of the municipalities and population. After the first five years of functioning, the leaders of this first Polish metropolis seem to be ready to adjust their metropolitan institutions, understanding its limits and searching for inspiration at the international level.