An analytical model of the true area of contact between molten metal and a rough, solid surface has been used to calculate thermal contact resistance and to predict how it changes with surface roughness, substrate thermal properties and contact pressure. This analytical model was incorporated into a three-dimensional, time-dependent numerical model of free-surface flows and heat transfer. It was used to simulate impact, spreading and solidification of molten metal droplets on a solid surface while calculating contact resistance distributions at the liquid-solid interface. Simulations were done of the impact of 4 mm diameter molten aluminum alloy droplets and 50 mu m diameter plasma sprayed nickel particles on steel plates. Predicted splat shapes were compared with photographs taken in experiments and simulated substrate temperature variation during droplet impact was compared with measurements.