What can a metal detector detect?

I am going to go to a concert and I am going to take my country's flag with me to show where I'm from and stuff and I read that they don't allow flags in the venue so I'm thinking of folding the flag and putting it inside my jacket and carry my jacket with me inside the venue but the thing is I don't know if when they check me with the metal detector thing when they patt me down if the metal detector will detect the flag so if anyone knows please let me know thanks

Metal Detecting Hunt