In this perspective we highlight the applicability of migratory carbene insertion reactions into TM–C bonds as a new tool for catalytic C–C bond formation. In Section 1 we introduce the reaction, wherein we also discuss the applicability of transition metal carbene formation from reactive carbene precursors. In Section 2 we summarise the available mechanistic information about this elementary step derived from stoichiometric model reactions. In Section 3 we review the available catalytic examples, with a focus on new developments in palladium mediated cross-coupling reactions (thus expanding the substrate scope with carbene precursors) and carbene polymerisation (allowing the synthesis of highly functionalised stereoregular polymers that are difficult to prepare otherwise). Recent developments in these fields in combination with the close analogy of carbene insertion reactions with CO (and alkene) insertions open up new possibilities for the development of interesting new reactions based on carbene insertions.