The frames made out of metal are the lightest and cheapest ones you can find on the market. A bed made out of this type of frame is easy to move around and even to adjust its size.
But, of course, if you get a bed that has the headboard and footboard connected to the bed, its size won’t be adjustable.
For this, you’ll need just the base for support. The base comes, in most cases, together with box springs.
Still, in case of bunk bed, there won’t be any box springs, just a set of bars placed to keep the mattress in place.