The terms matter and substance are generally said to correspond to hulê (usually set alongside 'form' or morphê), and ousia ('being'), respectively. It's worth mentioning that 'substance' is regarded by many as a Latin mistranslation of ousia, insofar ousia does not really mean anything like 'substance' in the sense that we generally understand it. Further, ousia and hulê ('substance' and 'matter') play very different roles in the Aristotelian philosophy, and do not function as pairs in a distinction. As far as mind (nous) goes, it corresponds best to the category of potentiality (dynamis, and not either matter or substance): "It (nous) has no other nature other than that of being potential, and before thinking it is absolutely nothing" (De Anima).

I might have this formulation wrong but I was wondering where in Aristotle is the distinction between matter and substance? For example, I thought he made the point that mind was substance but not matter? — DS1517

These references may be a useful starting point:

In Z3, Aristotle considers the claim of matter to be substance, and rejects it. Substance must be separable and a this something (usually translated, perhaps misleadingly, as “an individual”). — Aristotle on Substance, Matter, and Form

Ζ.3 begins with a list of four possible candidates for being the substance of something: essence, universal, genus, and subject. ... In the Categories, individual substances (a man, a horse) were treated as fundamental subjects of predication. ... This horse is a primary substance, and horse, the species to which it belongs, is a secondary substance. — Aristotle's Metaphysics - SEP

As StreetlightX notes, matter and form are the paired aspects of an individual (per hylomorphism). Substance can refer either to the individual (primary substance) or the formal class of things an individual belongs to (secondary substance).

Aristotle describes mind (nous, often also rendered as “intellect” or “reason”) as “the part of the soul by which it knows and understands” (De Anima iii 4, 429a9–10; cf. iii 3, 428a5; iii 9, 432b26; iii 12, 434b3), thus characterizing it in broadly functional terms. — Aristotle's Psychology - SEP

For Aristotle, mind is a formal characteristic of individual human beings in the sense of man is a rational animal. The term distinguishes human beings from other animals in a functional sense and is not intended to denote some kind of immaterial substance or property (say, per Descartes or property dualism).