Just An FYI:
This is going to be a tough one given that - that door looks as though it is one of the standard "Aluminum" doors that are attached to prefabricated/mobile homes . . . Just know that a majority of these doors are usually just aluminum frames filled with some form of installation and then encased with a sheet of aluminum on both sides . . . Also - Ya' should know that they are usually just a grandiose storm door made to look as if it is a regular wood style exterior door . . . Given this "You" have to first make the decision of whether or not it is really worth the time and effort to repair or replace that door . . .
Anyway, since it seems there is only that one spot where the door has been dented and the paint is pealing, let's go with repair/fix/paint . . . AND -
There are possibly 5 different ways to do that from the most complex to the easiest . . .
The one "You" do not want to do . . .
1) Strip door of all paint (using wire brush/sander - chemicals will not do a proper job), try pulling out dent and make any other repairs, lightly sand down door, power wash, wipe down with mineral spirits, prime door, then repaint door . . .
Then there is simply fixing/priming the area before painting the whole door:
(Given in detail since I think "You" probably are going to do this one . . .
)
2) Remove as much paint from specific areas as "You" can: "peel" away lose sheets of paint and if NEED be use a wire brush to remove any excess paint you can
(If Ya' do go the way of using a "Heat Gun" - be very very careful, the aluminum will heat up and can become very very HOT . . . So - Most of the paint should peal/come off and "You" will be back at the first suggestion . . . Also, DO NOT use while the door is still up or in the house); if there are any "holes"/"Cuts' in aluminum they need to be filled using an epoxy calk for aluminum or metal; lightly sand areas (gently blending the edges); wash the door well with a degreaser dish detergent (Dawn comes to mind); let totally dry; wipe down whole door with mineral spirits (Again let dry); paint door with primer, and then 2 coast of exterior paint or an all in one primer/paint product in the color of "Your" choice of maybe a dark flat color to hide any imperfections (gloss paint will only highlight the imperfections) . . . Sherwin Williams & BEHR are 2 of the best all in one out there . . . DONE - EASY PEASY . . .
The next way . . .
3) Don't worry about doing anything major . . . "Peel" what paint "You" can away from door; Clean very well with detergent and wipe down with mineral spirits to make sure the surface is free and clear of any dirt . . . Use All in One Exterior Primer & Paint as I mentioned "in a dark flat color to hide any imperfections (gloss paint will only highlight the imperfections)" or get crafty and "Sponge Paint" / "Leatherize" Door . . . "You" might also be able to use the New All-In-One Spray Paints that can be used on anything . . . VERY EASY PEASY . . .
Another way . . .
4) Prepare the door - "Peel" Paint & "Clean" Door - then get some "Adhesive backed" product and wrap the door as "You" might one of "Your" MODS . . .
(BTW: Ask "Rave" how to do this - remember she did her refrigerator and made it look as though it had "Marble Doors" . . . Just Sayin' . . .
)
Last and the easiest of all . . .
5) Wait until the spring and then when "BF" comes back have him do it - Or even better go buy a Used Exterior Door from somewhere like "Habitat for Humanity"
(BTW: It is where I got an aluminum exterior screen door for "My" apartment for only $10.00) . . .
Well - I hope this information helps . . .