The article provides a summary of the recent developments in using carboxylic acids and derivatives as aryl, alkenyl, and alkyl electrophiles for CH functionalization. This manifold exploits ubiquitous carboxylic acids as electrophiles after oxidative addition and decarbonylation in the absence of external oxidants under Rh, Pd, Ni, and Ir catalysis. Mechanistically, acyl RC(O)X bond oxidative addition to low valent metals is followed by decarbonylation, resulting in a net generation of R[M] electrophiles for a broad range of CH functionalization processes. The article covers aroyl chlorides, aroyl fluorides, anhydrides, carboxylic acids, esters and amides, and other related acyl derivatives.