The Micael addition is simply the conjugate addition of an enolate nucleophile to an a, b -unsaturated carbonyl compound. Protonation of the initial intermediate gives a chain-extended product. Any sufficiently electron-withdrawing group on the acceptor double bond will allow this reaction to proceed.
Examples are hydroxide, fluoride, and alkyllithium compounds.
Examples are iodide, thiolates, cuprates and enolates. The utility of thinking this way is that a hard nucleophile will react fastest with a hard electrophile, and a soft nucleophile with a soft electrophile. Take a look at a series of Michael acceptors. In these plots, the LUMO is mapped onto the electron density surface, so that the blue regions are the areas of best electron-accepting ability , while the red regions are not electron accepting.