If you have found a man you are interested in on one of your favorite online dating sites, I say go for it. Send the guy a message and introduce yourself. Appeal to his interests, and be sure to close with a question that moves him to action, one that requires him to respond.
I think the best way to start is by saying, “Hi, (his name). I’m (your name). I saw that we both love the same (band, book, food, travel destination). I would like to know more about you. Are you currently seeing anyone/have you ever seen (favorite band) in concert/did you know there’s a sequel coming out to our favorite book?”
Keep it short and sweet. You want to give him just enough information to spark his interest, but not enough to bore or overwhelm him.