Decide on the section of the patio door's metal frame where you want to drill the hole: on a bottom edge or on the side where you grip the door to open it. Measure the width of the door's metal frame to determine how big the diameter of the drill bit should be.
Place the metal drill bit into the opening in the end of the power drill. Close the opening with the locking tool on the drill.
Wipe off the section of the door's frame where you will be drilling with a water-moistened paper towel to remove loose dirt and contaminants.
Close the patio door. Slide the locking lever or turn the locking latch to keep the door closed. Plug in the power drill and on work gloves and protective eye gear.
Press the trigger on the power drill. Place the rotating drill bit against the metal frame on the patio door at the point where you want the hole to be. Push the drill bit through the frame. Pull the drill bit halfway out of the hole once the it has been pushed through. Push the drill bit back through the hole. Repeat this two more times before pulling the drill bit out of the hole.
Release the power drill's trigger. Unplug and remove the drill. Unlock the patio door and open it.
Clean the loose metal dust from the frame on both sides of the patio door -- use a water-moistened paper towel for this. Clean the floor on both sides of the door underneath where you made the holes.