When can I use the expression "I'm telling you"?
Native speaker’s answer
Rebecca
"I'm telling you" is an expression that is used to emphasize what is being said is true. Chandler is telling his friends that the situation he is in is the same as when his parents got a divorce. Ex: I'm telling you, I met Tom Cruise! Ex: I'm telling you, I went to Italy this summer. I have pictures to prove it.