Selective radical capture remains a central challenge in transition metal-catalysed transformations involving multiple radical intermediates. Now a ligand-modulated metal–radical polarity-match mechanism exploiting electronic bias for selective radical capture has been identified. This principle enables general photoredox/copper-catalysed 1,2-dicarbofunctionalization of ethylene, providing modular access to structurally diverse 1,2-dicarbofunctionalized ethanes.