Hello friend here I am for the riddle, I see you have musical tastes... let's say.... quite metaphorical.
The clue: it has to do with the X-Files. Let's see how I relate all this. The outside, that which is alien, that which is here and we don't see? Unknown creatures that can take our world away from us, perhaps?
The three songs you've left below have something in common, self-love, which should be kept under lock and key. It should never be touched, it can never be lost.
Maybe I've hit the nail on the head. Each of your musical proposals with its own particular way of saying. But at the end of it all I had fun and I didn't know this song by Sheryl. I like it.

I don't know why listening to these songs I thought of Jim Morrison. Maybe I'll get up the courage to write a really dark poem.