Most soups freeze quite well - but I've found that chunky veg ones rather than blended ones don't do quite so well. Also, if it's a cream soup I think it freezes and reheats better if you freeze it without the cream.
What kind of soup is it?
I freeze mine in tupperware containers and usually defrost and reheat in the microwave. My mum does the same and she's been making soups for years!
I usually freeze mine in tupperware, but I suppose freezer bags would be OK. Best to let it defrost before cooking as it's better for flavour and either micro or pan heat. Depends on the ingredients as well. What soup it it?
you can freeze it in any kind of container you like just leave a bit of space at the top for expansion. Id defrost in the mic and then move to a hot setting to warm it up once its defrosted. Or defrost overnight in the fridge and heat on the cooker.
put it into a frezer bag leaving an inch gap at the top, then put it into a container so that it freezes in a proper shape and doesn't just go blobby in your freezer and take up lots of room. Once it's frozen in to the right shape you can discard the container.
Take it out of the freezer a good hour before you want to use it then just squeeze it out of the bag in to a saucepan on very low heat in to which you have put a tiny bit of water so the soup doesn't scald and then put the lid on the saucepan and geat gently.
It's best to freeze soup with out cream or yogurt or any high fat dairy in it and add this as it comes to the right temperature as it could split during reheating