Spin models in statistical mechanics have a history of almost one hundred years. They first occurred as models of ferromagnetism and Ernest Ising's PhD thesis. In this minicourse we will start with a brief survey of some results in the Ising model. We will then turn to its mean-field version the Curie-Weiss model and see how phase transition can be proved there. In a final step we will introduce some simple models of so-called spin glasses and discuss some of the results that have been proved in this context.