The inclusion of exact-exchange contributions is fundamental for an accurate description of the electronic structure of metal-organic interfaces. The performance of standard DFT functionals, comprising LDA, GGA (and hybrid) functionals, is strongly limited by the Coulomb self-interaction error (SIE). In fact, they describe reasonably well extended metallic systems (where the SIE is small), but show several drawbacks for molecules. As a result of this unbalanced description the energy-level alignment at metal-organic interfaces if often wrong and an incorrect description (eg charge-transfer) is achieved. Proper incorporation of exact-exchange contributions through the use of effective exact-exchange approaches eliminates the Coulomb self interaction error and allows a correct description of the energy-level alignment, thus resulting in a strongly improved description of the metal-organic system. However, because of …