[kdlynn (OP)]

... or is that impossible?

[Mirage]

Kadie asked me to add this picture

[kdlynn (OP)]

thank you, dan. that's the car i'm sitting next to. my car has a tiny rust spot... but how can i prevent that from happening to my car?

[elegantlywasted]

I was told that you should paint (with auto paint) the rust spots. This wont stop it from spreading but it slows it down alot.

[dentstudent]

Using automotive products, there are some that reuce the spread of rust. One I remember was called ....er, I'll send you a pm. The only sure-fire way is to completely remove the rusty bit and have some new metal/fibre glass replacement.

[eric l]

The picture clearly shows that there is already rust formation beneath the paint too :  the film of paint is pushed up by it. 
To start, you will have to remove the rust either chemically or mechanically (e.g. sanding paper and a lot of elbow grease).  With the sanding paper, you have to go at least 1 cm beyond the blister where the paint is pushed up by the rust.
Then a good primer (anti-rust) and finally the lacquer.

[kdlynn (OP)]

well i'm glad i don't own that car then!