The study deals with the politics and history of the European Metalworkers' Federation. With 80 member organizations and nearly 6 million represented workers, the federation was the most significant industrial trade union confederation in Europe. Its activities have multiplied and diversified in many areas of action due to the European integration push of recent decades. The work is guided by the question of whether these developments have transformed the federation from a European interest association or a lobbying organization of national trade unions into a transnational trade union organization with its own capabilities and means to enforce workers' interests.