Here are a couple common English idioms used when talking about fashion:
⁠They're certainly dressed to kill.
⁠He's definitely dressed to impress.
⁠She's dressed to the nines tonight.
The three idioms above are used to describe someone who is dressed up very nicely. You'd most likely use them to describe someone wearing formal clothing like a suit or dress.
⁠I wouldn't be caught dead in that shirt.
You would use this last idiom whenever you want to say that you would never wear something. In the case of the example above it means: ⁠I would never wear that shirt..