When we lick a cold pole in winters why our tongue sticks to it

Dear student,
Please find below the answer:

Our tongue is warm. According to the principle of calorimetry, when a cold piece of metal (pole in this case) touches the tongue heat will transfer from cold body (metal) to hot body (tongue). Metal is a good conductor of heat and hence pull the heat away from the tongue which makes it to stick with the tongue.  

Hope this clears your doubt.
Regards.