There are a lot on the market and so
can be quite baffling.
Things to note when comparing them are :
* That the spike into the ground is at least 12" long because any less makes it too unstable.
* That it has more than 4 'arms' to hang feeders from - you don't want to have to be buying additional ones (however, i did order some brilliant 'hooks' which will attach to any 1" diameter host), 6 'arms' i would call a minimum.
* That the main pole is an inch diameter - any less and it's too flimsy.
I usually recommend the Gardman brand, the Tom Chambers brand is another good one.
You definately get what you pay for but the former often is on offer in garden centres, so worth going to a few to see and compare what's available near you - actually, you could google it all i suppose !
I know your question is specifically about metal, shop bought feeding stations but don't forget that trees and woody shrubs can also be used for hanging feeders from

Don't forget also that siting stations is important close to trees and tall shrubs - birds need shelter/cover to dart into when danger's around.