What is considered mainstream or normal in terms of gender, sex, and sexuality is heavily influenced by the stories our societies tell themselves. Our concepts of sexual relationships, beauty, appropriate displays of affection, and how to perform our gender (i.e. what looks or behaviors make a 'real' man or 'real' woman) can be shaped a lot more by television, radio, books, social media, and film than by science or even our own lived experiences. In order to fully understand gender, sex, sexuality and all the things that go with it, it is important to understand how these concepts are displayed in the media and what that says about our culture as a whole.
Always remember that how a piece of media represents gender, sex and sexuality will change depending on who created it, why it was created, where it was created and when it was created.