Feeling butterflies in your stomach. Saying that “you feel butterflies” around someone or that a person “gives you butterflies in your stomach” are a good way to tell if you have chemistry. We’ve all felt it at some point, if we’re lucky — a feeling that isn’t normal, and usually only happens when you’re in the presence of someone with whom you’ve got a strong attraction. It comes on suddenly, because that’s how attraction works. If you feel those telltale butterflies, you’ve got chemistry.