Psalms is one of the oldest prayer books in the world, y’know.
The psalms—yep, the very same psalms we find in the book of Psalms, as well as various random psalms we find elsewhere in the bible—are sacred songs to and about God, used to worship him. A lot of ’em are addressed directly to God. As such, they’re prayers.
Hence Jews, Christians, and Muslims have used ’em
Likewise, because they’re bible, they’ll help us understand God better, and show us we can pray the very same things we find in the psalms. Including all the stuff Christians balk at: “Are you sure you can pray such things?” Yes you can. If it’s in the psalms, you can pray it. You can
Really, those people who feel they’re limited in what they can pray, get that idea because they haven’t read the psalms, or don’t think of psalms as praise and prayer. They imagine ’em as nice poetry (or odd poetry,
(And once you memorize some of the shorter psalms, you can brag how you’ve “memorized entire chapters of the bible.” ’Cause technically you have.)