The '80's was trendy in its own way, and so was the '70's, and so on.
Let's face it, the younger generation will always be thought of as trendy and listening to junk music by many from the older.
So, if a friend of yours asks "explain (rock music, metal, punk or any combination thereof) to me," the best thing to say is that all you have to do is listen...if you don't like it, then it's not for you. Live and let live.