Foundry & Hovels should be good for metal crates, barrels etc. if you’re happy with traditional 25mm sizing. Otherwise, metal scatter seems a bit thin on the ground with the demise of Thomarillion & Otherworld. Hopefully, the fab 28mm-ish scenics from the latter will resurface with another company in due course.
Ainsty Castings & Dunkeldorf Miniatures might be worth a look at for metal set dressing bits & pieces.