Possibly one of the most problematic places to install a ceiling fan, is metal awnings. The problem with installing ceiling fans in metal awnings, is that unlike a standard awning, there is simply no wood member to attach it to.
Also the power supply has to run and in a metal awning it will have to be exposed because there is no attic space to conceal it in. So then lets get started understanding how to overcome both of these problems.
Your first job is to get an electrical line to where ever it is that you plan on hanging your fan and then attaching it to a junction box. You see, in the end your fan is going to have to be hung off of a junction box.
Of course the best way to sidestep running a power line all together, is to simply opt for a solar powered ceiling fan. The solar panel can simply be mounted on the roof directly above the ceiling fan and the power line ran directly down to it.
However; if you choose to go with a standard ceiling fan, you're going to have to go up in your attic and tie into a power line. Usually any source of power will work, so simply find one and splice into it. Do shut of the main power at the box first though to avoid being shocked.
Once this is done, run the line to the outside wall that's adjacent to the awning and then drill a hole through to access the awning. Now any line that's ran outside must be encased in metal conduit, so make sure that you pick some up at your local hardware store.
So now you're stuck with the problem of attaching your electrical junction box to the roof of your metal awning. Of course you could simply drill some holes and screw it in place but that would leave the tips of the screws popping out of your roof.
The best simple solution is JB Weld. It's a two part metal adhesive that you can buy at your local hardware or auto parts store. It comes in two separate tubes and each part has to be mixed together in equal parts. It's strong and very durable.
Use a liberal amount to literally glue the metal electrical conduit box to the metal awning after you have sanded off the paint where it's going to be attached. Then use a long stick running to the ground to press the conduit box in place until it cures.