This chapter frames the study within debates on the territorial dimension of politics in the age of globalisation. It argues that, while much attention has been paid to regional and rural–urban divides, intra-metropolitan fractures remain understudied despite their growing significance. The chapter outlines the rise of a new cultural conflict—the “transnational cleavage”, opposing GAL (green–alternative–libertarian) and TAN (traditionalist–authoritarian–nationalist) values—and links it to polarisation within European metropolises. It sets out the central research questions: whether metropolitan public opinion and voting behaviour have polarised alongside the emergence of this cleavage, and which compositional and contextual factors account for such trends. By positioning metropolitan areas as key sites where globalisation-related cultural conflicts manifest, the chapter advances the thesis that metropolitan polarisation represents a distinct territorial expression of Europe’s new cultural cleavage.