Understanding dislocation mobility is key to understanding material strength: how materials deform and the energy required to do so. An important unsolved question in this regard is whether dislocations can accelerate to supersonic speeds in metals. Previous molecular dynamics (MD) simulations in cubic crystals have indicated that supersonic motion may be possible in some cases. Our own work continues this endeavor for new crystal geometries using both MD and theory for an improved understanding. In this talk we present recent results, both analytic and from MD simulations, that elucidate high speed dislocation motion in single crystal metals under various conditions.