Do you know that the tongue is a muscle? It is the only muscle that is attached at one end and open on the other.
The tongue is interesting. It can get in the way of great singing. Most of the time it should simply relax and touch the tip of your bottom teeth.
It has to move around to help you form consonants like t, th, k, g, c, d, and more. Then it needs to get out of the way so you can make a nice tone with your singing voice. It needs to relax and stay out of the way so the vowels can form properly and create a nice tone.
Next time you’re singing, think about what your tongue is doing? Is it getting in the way?