Leibniz' monad is the fundamental substance in his ontology. Universals may be induced through rational contemplation, but the individual substance exists independently. Thus, the two concepts are similar in that the fundamental nature of substance is finite and discrete, as opposed to infinite and continuous, as many other philosophers maintained. Another fascinating comparison between the two systems is concerned with life and movement. Aristotle describes three types of psyche or soul, that which gives life and self-movement to living substances, and in living things is the form of that living thing.
Plants possess vegetative souls , allowing for nutrition and reproduction.
Animals possess animal souls , which allow for nutrition, reproduction, and sensation. Humans possess rational souls , which allow for nutrition, reproduction, sensation, and reason. Leibniz, on the other hand, distinguished between three types of monad. Rational monads possess self-consciousness, reason, speculative ability, etc. The similarity between these two hierarchies of forms, if you will, is clear.