What should you do when something needs to be done? Should you paint the door, or clean it off and polish it with a good furniture polish? What if your door is metal, what then, and how can you clean that messed up kick plate?
For metal doors it will be easiest to clean if you remove it from its hinges, place carpet strips or old towels on saw horses. The strips or towels will protect the inside of the door from damage. Then get a bucket of warm water and a gentle household cleaner and use a soft bristled brush to scrub the door.
The metal kick plate should probably be replaced, and there are three methods used to attach the old kick plate: magnetic strip, peel and stick backing, or screws. The peel and stick backing may not come off easy, and if that is the case just wash it and after you've completed cleaning the door put a new kick plate over the old one.
If the door is badly faded you may have to prime it first. Either use masking tape to cover the door hardware or remove the hardware. If the door has a chalk like film it will be best if you use an alkyd primer, but if it is only slightly weathered use an acrylic primer. Use exterior grade-one primer. Bondo or DAP CrackShot Spackling Paste are good products to fill in scratches or dents. Sand the filler smooth and prime the filled surface.
Then the door will need to be painted with acrylic gloss or semi gloss trim enamel. To achieve the ultimate in a smooth finish lightly wet-sand the first coat with waterproof sandpaper 800 to 1100 grit. Wipe the door clean and when dry apply the second coat. Then install the new kickplate and your door is good to go.
You could do the inside of the door in the same way and finally install a new weather-strip after you've removed the old. Remember this procedure is for metal doors.