Anyone know if there are any restrictions on carrying metal containers in carry-on's or checked baggage?

Our toddler has a stainless steel water bottle because we try to avoid using plastic when possible (due to leaching, etc.). Would prefer to carry on the plane but can check in with luggage if necessary (or allowed).

A couple years ago we had to throw out an empty, unused camping fuel container at check-in. Not sure if there would be a different logic for allowing/disallowing a metal water bottle.

We'll be flying Qantas from Australia, then Southwest and Northwest within the U.S.

Thanks,

Ozgal