Moq
Wait, you are going to compare us normal folk to David Hamelech and Michal?! They were on a supremely high madreiga and were Baalei Ruach Hakodesh. Who really knows what that love means. Go check the Radak or some other Meforshim I’m sure someone goes into it.
Furthermore, you can love someone without being married. But at the minimum you have to know the person or know a lot about them. (Michal knew all about David, and maybe had met him as he was quite famous and a best friend of her brother Yonasan) The Rambam translates love as the emotional pleasure a human being experiences when he understands and focuses on the virtues of another human being.