The key to hanging anything in cement or metal is to have the correct anchor. You also want to know the basic characteristics of the concrete or metal you are anchoring your curtain rods to. For example, knowing how old the cement wall is will tell you how hard the cement is (cement hardens with time). It would also be helpful to know the thickness of the metal you are dealing with. Having this information will help the project progress smoothly.
Anchoring to Concrete
Mark the concrete where the curtain-rod hangers will be anchored. Place the hangers against the concrete and mark where the holes need to be drilled for the Tapcon screws. Tapcon screws work well for concrete.
Place a concrete bit into a drill and drill pilot holes into the concrete at the places marked.
Place a Philips-head drill bit into the drill. Using the drill and Tapcon screws, anchor the curtain-rod hanger to the wall. Repeat for the other hangers.
Hang the curtain rods and curtains according to the directions supplied with the rods.
Anchoring to Metal
Mark the metal where the curtain rod hangers will be anchored. Using a self-tapping screw and a drill, begin drilling the screw into place. The screw will spin on the surface of the metal until the screw drills through the metal. After the screw penetrates the metal, allow the screw to sink into the metal half of its shaft length. Remove the screw from the metal.
Place the hangers against the metal and, using the same screw as before, anchor the hanger to the metal. Place as many self-tapping screws through the hanger as are needed. Repeat for the other hangers.
Repeat Step 4 under Anchoring to Concrete.