This chapter analyses how compositional and contextual factors shape voting for GAL and TAN parties within metropolises, thereby exploring mechanisms behind the metropolitan polarisation of the vote. Drawing on an original dataset that combines electoral and contextual indicators, statistical analyses reveal that contextual effects matter independently of socio-demographic profiles. Geographically and socially peripheral metropolitan environments—such as those characterised by greater distance from the central railway station and disadvantageous housing market dynamics—are associated with higher support for TAN parties, while central contexts favour GAL parties. However, the determinants vary across cases: for example, the ethnic structure of boroughs strongly predicts TAN support in London but not in Rome. Although this ecological analysis does not allow for causal inference about individual behaviour, the findings demonstrate that metropolitan contexts exert distinct political influences, suggesting that “where one lives” matters for voting patterns. Therefore, the chapter underscores the importance of compositional and contextual dynamics as complementary factors in explaining why metropolitan political geography reflects the transnational cleavage.