I know the first scene of the movie starts with a car driving in the pouring rain at night. The car breaks down and people somehow end up outside in rain.

More help pleaese, was it an old movie, how many people in the car?

Well, that is very vague, but there is that scene at the beginning of

Identity (2003) (http://www.imdb.com/title/tt0309698/)

Please do not rate this answer if it is wrong. just trying to help with a very vague description :)

Maybe Rocky Horror Picture Show? They are driving in the rain in the beginning and end up walking for help after their car breaks down.

Haha, yeah that's it... Rocky Horror Picture Show. A must see.

YES finally someone with an open mind. Around here I can't even get someone to watch it but I really enjoid it and wold like to find it on dvd:D