be a/the/(one's) knight in shining armor

To be a selfless, chivalrous person who helps someone in distress. Typically used in reference to a man who comes to the aid of a woman. When the police officer pulled over to help the old woman change her flat tire, she hugged him and said he was her knight in shining armor. You don't need anyone to be a knight in shining armor. You need to be the one who takes care of yourself first and foremost. Thank you for catching that spider! Ah, you're my knight in shining armor!