Galaxy clusters are the largest structures in our Universe, roughly one thousand times the mass of our Milky Way galaxy. Clusters are filled with an atmosphere of extremely hot (10^8 K) gas which radiates profusely in x-ray emission; x-ray telescopes thus provide a wealth of detail about these objects. Modeling this gas is essential to understanding how the most massive galaxies form in our universe. Though this hot gas is an ionized and nearly collisionless plasma, most models to date have treated it as an ideal gas. I will discuss a new method to simulate the formation of galaxy clusters which includes plasma appropriate to this hot gas, and I will show how it changes models of galaxy formation. In particular, I will focus on convection in the hot gas: while clusters have traditionally been assumed to be convectively stable, including the correct plasma physics in fact implies that they are convectively unstable. This convection radically changes how metals and gas are distributed throughout the cluster, and may significantly impact the mass estimates of clusters which are used to constrain dark energy and cosmology.