Trump and Melania lead completely separate lives. They don't even live together. He whores around and when he needs a wife for an event, he calls on Melania. Personally, I think that if he hadn't won the 2016 election, he would have traded Melania in for a newer, younger model. But he couldn't get divorced while he was president and now he can't divorce her because he wants to run again.

The relationship works for them because they both got what they wanted. He wanted a model for a wife and she wanted a rich husband.