NO adsorption on metal surfaces has been studied extensively due to its important role in many catalytic processes. In the past, it was recognized that the tendency for a metal surface to dissociate NO depends on its position in the periodic table, but little was understood about the dissociation process itself. Recent experimental and theoretical studies have shown that this view is oversimplified. In addition to the distinction between molecular and dissociative adsorption on surfaces, the structure of NO on metal surfaces has also been the subject of detailed study and debate. It is therefore timely to update our ideas about NO adsorption and reactivity. Here we examine the structure of NO on surfaces, in particular the break-down of vibrational assignments and we look at how these assignments can be improved. The NO dissociation process is also discussed along with the formation, and reactions, of the NO dimer, (NO)(2), on some metal surfaces.