Around section 67 of the Monadology, Leibniz firmly embraces an object-oriented ontology (it is a monad-oriented ontology where the particulars are individuated with respect to the rest of the world, but the rest of the world itself boils down to monads.) Matter is made of monads all the way down and a mind relates to a body only when we consider a single layer; the body itself is made of monads and some matter and this matter is itself made of monads and some more matter and so forth. This recursive operation could also be used by the materialist who would take a mind to be composed of matter and further minds and so on. In any case, it is a thoroughly infinitist ontology. Each monad is singular and everything is full of them - Leibniz panbiosis insinuates a chain of beings that points towards some form of recaptulation thesis where more of the same (not quite the same) is found when we look for what is inside.
Interesting to consider the Leibniz scheme in a Nick Land / Brassier / Nigarestani environment. Monads long to become matter - in their own singular way they thrive for composition that would render them unnecessary. Like a clock-maker who aims to be perfect enough to afford to leave the stage (Leibniz´s God, who seems often to want to disappear in the cogs of the world). Monads entwine a death drive in their dealings with life: mattter is something to aspire to. They compose bodies because they want to dissolve in a world and yet matter is never fully realised as further layers of monads ever appear. The will for anihilation is perpetually postponed, deferred, left for the next layer. The state of pure matter is unreachable.