Tongues can and do really stick to poles when it's freezing cold outside so I would not recommend you doing so as I can personally attest to getting my own tongue stuck to a pole in my younger days when I was 5 and someone dared me to do it.
I don't remember the temperature of the weather outside but it was likely 30 F at least and the fire department had to be called to remove my tongue from the pole.
The fire department used some cool water to help my tongue come unstuck from the pole and had me breathe on the pole.
It was really scary for me and I would never do it again.
Your tongue could likely stick to a metal pole as long as it's at freezing temperatures outside.