Where does the fat from hamburgers drain?

It doesn’t. As far as a mess, just keep a plate under it. Honestly, I like that it doesn’t drain. Cooking in that fat makes it tastes better and less likely to burn.

Is this easy to clean? Can it be immersed?

Dragons3.....I have found it extremely easy to clean. NO, it can NOT be immersed. I personally use select-a-size paper towels to clean my unit each time I use it. Immediately after removing my food I unplug the unit then use one small paper towel to wipe it down. I then I take that same paper towel and rinse it with soapy water and while still damp (not dripping) I lay it in the unit and close the lid and allow it to 'steam clean' for about 20 seconds. I then discard that towel, and use a fresh one dampened and wipe the unit to 'rinse' it. The unit is still 'hot' at this point....I use tongs to hold the wet paper towel. After rinsing, I use one last small paper towel to dry the unit, then set it aside 'open' to cool. I 'never' use spray of any kind on my unit and have had no problems with foods sticking. It's really a great little gadget. I also have the Dash Mini Waffle Maker....absolutely perfect together! Mine get a lot of use....highly recommend both.

Can it cook steak? How can you tell when it's medium rare?

Fortunately, you can cook steak on a griddle whatever the model you have available. In fact, cooking steak on a griddle is no more difficult than cooking it in a frying pan or on the barbecue. So, however you like to eat it, delicious and juicy steak can be just a few minutes away if you own a griddle