Spectacular progress has been made recently in molecular graphics and, more generally, in computer-assisted chemistry techniques, which nowadays enables the chemist or biologist to design new processes or to create novel compounds with yet unknown properties, such as drugs or catalysts. After a brief review of the present state of the art in basic molecular graphics applications such as the representation of structural models and the construction of three-dimensional molecular surfaces as solid models, this paper will concentrate on the evaluation of intermolecular interaction energies for organometallics using a new theoretical model we have developed recently. Calculated as the sum of electrostatic, charge transfer and exchange repulsion components obtained from extended Hckel wavefunctions, these energies are then used as a reactivity index and mapped according to a colour code on to the molecular surfaces of organometallic substrates. This model is shown to predict adequately the initial stage of attack for kinetically controlled mechanisms such as electrophilic or nucleophilic addition reactions to the substrates, as demonstrated by several examples ranging from the protonation of ferrocene to the attack of 1,3-butadiene-Fe(CO)3 by the H? anion, which allows us to rationalize the high regioselectivity generally observed in these reactions. Finally, a discussion is made of the possible developments of the model so as to make it a routine tool for a general molecular graphics approach of organometallic reactivity.