Galaxy clusters are the most massive bound objects in the universe, and understanding their structure and physics is crucial to physical cosmology. My talk will begin with an outline of how strong and weak gravitational lensing signatures are used as a tool to study cluster structure. I will then discuss several facets of our theoretical and observational research in this area.One topic that we will consider is how baryonic physics impacts on the lensing properties of simulated clusters, in particular the importance of feedback from the black holes hosted by cluster galaxies. This impacts on observables such as the abundance of giant arcs.Bullet cluster systems that have undergone violent mergers in the past offer a unique window on dark matter, and allow us to test gravity on large scales. We will focus on Abell 2146, a unique system that we are currently investigating.