I will explain how unitarily invariant matrix models can be solved in a large N (formal or asymptotic) expansion, using Dyson-Schwinger equations. After analytic continuation, these equations can be brought in the form of abstract loop equations, which are particular form of Virasoro constraints attached to spectral curves. The general solution of these equations can be described in terms of topological recursion. We will give a few examples of models which have been treated this way. The lectures will also serve as background material for the lectures of Raimar Wulkenhaar.