This is possible because when water touches a hot surface it evaporates. This evaporation creates a gas which will lift the water droplet above the heated metal preventing it from evaporating immediately. This is called the "Leidenfrost effect". When put on a jagged surface like the example on the screen it will allow the gases to collect forming enough lift to lift the water droplet up and making it move forward. This may seem impossible but look at this video:
