Detachment and absorption are two of melancholia's fundamental features. In this paper I try to demonstrate that these features can be productively connected to philosophical thought. I do so by focusing on Leibniz's fundamental metaphysical entity, the monad, which I interpret as revealing a melancholic configuration. My reading explores the special structure of the monad's encounter with the world, arguing that the structure of the Monad exemplifies the possibility of a productive relation between its utter closure and its philosophical openness to the world entailed in its activity of constant expressing of the world. This relation, I suggest in conclusion, manifests the structure of a metaphysics of mood.