How can we study the notion of structuralism in the framework of contemporary Anglo-Saxon metaphysics? After having briefly justified the ontological enterprise in the introduction, we will answer this question by starting from a classical ontological system, namely the "ontological square", a system inspired by Aristotle and taken up by a contemporary author, E.J. Lowe. This system structures reality according to two distinctions, namely the distinction between universals and particulars on the one hand, and between substances and accidents on the other hand. Now, structuralism seems to come from a criticism of this system. We thus criticize this ontological square by taking inspiration from B. Russell and D.W. Mertz: the only ontological category that exists is, in our eyes, that of particular relations. It is from this notion of relation that the notion of structure comes (a structure is a set of relations). Our conclusion will then be the following: only particular structures exist, and, to exist, for a structure, is to manifest an identity of its own by linking elements in a certain dynamic.