Popcorn can be a healthy snack if you prepare them properly. The best way to cook is air pop the kernels, then season them with a bit salt and (or) extra virgin olive oil.
You can also make popcorn with microwaves which is quick and convenient as all the ingredients are packed in a microwave bag. However, the lining of the microwave bag contains a chemical called perfluorooctanoic acid (PFOA) which can cause infertility. Also prepacked microwave popcorn tends to contain artificial flavoring, which is not healthy. So if you want to make the popcorn with microwave, use a glass container and season them yourself.