using my blackberry storm as an mp3 player?

[Jessica B]

I don't have an mp3 player or an ipod. I have downloaded slacker radio on my blackberry but I would like to know if it's possible to put songs on my blackberry storm like it's an mp3 player or an ipod or something. If i can do this for free, great, if i can't, that's cool too but i cant find any sites that let me download songs straight onto the phone.