knight in shining armor, a

A selfless, chivalrous man who helps a woman in distress. 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.

A rescuer or defender, as in What this political party needs is a knight in shining armor to change its tarnished image . This metaphoric expression alludes to a medieval knight. [Mid-1900s]

A rescuer or deliverer. This term, which recalls the age of chivalry through the image of a dashing knight on horseback clad in polished armor, dates from the sixteenth century but has been in figurative use only since the mid-twentieth century. John Ciardi pointed out that the phrase has been used with two meanings: the “Mr. Right” of a young girl’s dreams, rescuing her from the humdrum with the promise of romance, and in politics, the idealistic reformer. One might add a third, the white knight of the modern-day corporation, who rescues the company from a hostile raider and averts an unwanted takeover. Quite figuratively, the poet William Rose Benét wrote, “Like a knight in glittering armor, Laughter stood up at his side” (“The Last Ally”).

A wonderful guy. Fairy tales chronicled fair maidens in distress who were rescued at the last minute from dragons and ogres by a gallant knight in gleaming armor, where-upon they all lived happily ever after. Even if a young woman didn't view herself as a princess or consider herself in desperate straits, she still imagined herself being carried off by the man of her dreams, Prince Charming, a knight in shining armor.