As da01 mentioned a good 12 volt drill should manage this just fine if you are using a drill bit designed for metal.
How to install a chain lock on metal door.
Tape up the template for the lock plate.
Install a deadbolt lock to a steel door with help from a home improveme.
I have had metal doors on my last three houses and all were easy to drill.
I ve tried millions of things to get a hole in the steel door.
The locks consist of two sides the secured side where the chain is firmly bolted and permanently set then the sliding side where the knob at the other end of the chain can be inserted and slid into place.
Adding a deadbolt lock can be a great way to improve the security of your steel door.
If you do not have a deadbolt on the door place it about three to six inches above the door handle.
Move the fixed peg portion on the door face where the swinging arm easily.
Position the lock with the swinging arm portion on the door frame near the edge with the arm extending over the door.
Also if possible use minimum 10 screws butit s always best to take the latch to the hardware store to get the correctscrew sizing.
For the door side screws with a length1 8 to1 4 shorter than the thickness of the doorwill give the most strength.
I m tring to install a chain lock on the inside of my home.