Migratory insertions of alkenes into metal–carbon (M–C) bonds are elementary steps in diverse catalytic processes. In the present work, a radical-type migratory insertion that involves concerted but asynchronous M–C homolysis and radical attack was revealed by computations. Inspired by the radical nature of the proposed migratory insertion, a distinct cobalt-catalyzed radical-mediated carbon–carbon (C–C) cleavage mechanism was proposed for alkylidenecyclopropanes (ACPs). This unique C–C activation is key to rationalizing the experimentally observed selectivity for the coupling between benzamides and ACPs. Furthermore, the C(sp²)–H activation in the coupling reaction occurs via the proton-coupled electron transfer (PCET) mechanism rather than the originally proposed concerted metalation–deprotonation (CMD) pathway. The ring opening strategy may stimulate further development and discovery of novel radical transformations.