Preferably a metal one, with nothing under the bed (like a table, another bed, etc.)
a wooden bed with headboard
No. You're already on the internet posing the question, YOU do the research for YOUR project, and ensure it meets YOUR criteria to YOUR satisfaction.
The support strength should be more than double of a twin bed, because it not only has to support the double weight of two people, but the activities of two people in a queen size bed.
The only company I know of that sells queen sized loft beds only sells them in wood. That company is National Furnishing. Most metal loft beds have something underneath them for support, because metal loft beds are not that sturdy, similar to metal bunk beds. Good luck in your search!
