It is perfectly A-OK with the TSA to fly with a metal water bottle (or as my husband calls it "a water carrying system"). The qualifications are that it HAS to be empty, the lid has to be off of it, and you have to have it out of your bag and in the bin when going through the security check points.
I flew last month with my 40 ounce stainless steel Kleen Kanteen and had no problems at all! So happy travels in these next two months of traveling craziness!
1 hour ago