This is a molten metal effect I worked on recently. I started with a plane and then built a shader that causeed it to ripple. I then painted a few layers of textures to get the look I liked. After that I created a distortion effect to give the appearance of heat waves. I also created a flow map in Maya and then used that to get the steam looking the way I wanted it to. Lastly I made a fluid actor so that when an actor falls into the pit the metal would ripple.