I want to paint my front door......

https://www.valsparpaint.com/en/how-to/interior/special-challenges/metal.html

http://www.house-painting-info.com/articles/painting-a-steel-door/#.WgoQNVKZPVo

I would give it a light sanding and then paint it with a good primer. Tape off the windows and paint with exterior paint in semi-gloss or gloss.

If the current paint is in good condition... then just prime and paint over it... if the paint is cracking or peeling then you will need to strip it and start over... the EASIEST way is to take the door off the hinges and lay it flat.

You can strip it with either a chemical stripper or using a heat gun.. both with require a putty knife or scraper and then steel wool or sand paper or both...

A good quality primer for metal surfaces and good quality paint. ( I hope you choose a FUN one)

I am going to have to repaint our front door this year.. I used latex house paint on it 2 years ago when we repainted the house... the paint is now cracking and peeling off of our metal front door (the door faces west) and the 114 degree plus temperatures have taken their tole. I plan on stripping the door... using a HIGH heat primer or a primer for bar-b-ques and then a high heat paint (like for car engines) ... I just need to decide what color...maybe Turquoise.

Go to DIY and ask about primer for steel door, they will put you right.

would prime first and sand any rough spots first

Priming and then we use the Rust-Oleum. You know a door color doesn't have to be plain color, you could even do a mural on it to add that extra finesse maybe like a bouquet of flowers.

Turquoise and coral are my favorite colors. Either would be attractive if you love those colors, or choose another. 😇