Struggling Authors

Greetings to the forum.
I was wondering what to do about certain words used in a sentence such as: paper grenade or confectionary bliss ? Should they be just left alone or italicized; or shoud I use qutotation marks around them? Thanks for the assist!

I would love to be that intelligent but unfortunately I haven't got a definite answer.
My gut instinct tells me though that they should be italisized.
Good luck mad tee