Alignment of metal and molecular electronic energy levels at electrode-electrolyte interfaces is investigated using density functional theory. Three different regimes exhibiting qualitatively different energy level alignments are observed. The regimes are roughly defined by the size of the metal work function relative to the ionization potential and/or electron affinity of the electrolyte. It is demonstrated that proper matching of these quantities is essential for successful ab initio modeling of electrochemical interfaces and it is further discussed how such matching can be obtained by careful tailoring of the interfacial atomic structure. (C) 2012 Elsevier B. V. All rights reserved.