Used to express that something rarely, hardly ever or seldom happens.
めったに + Verb[ない-form], めったに + い-Adjective[ない-form], めったに + な-Adjective[じゃない/ではない-form]
Long explanation:
The ~めったに~ない grammar point is used to express that something rarely, hardly ever or seldom happens. It is a negative expression and always needs to be used with ~ない (negative form) at the end.