Is it correct to say "there be..."?

I’m currently reading Tolkien’s The Lord of the Rings. One sentence says:

[…] where there be mountains of gold, they say.

English is not my mother tongue, but I’ve found the same expression somewhere else, probably in song lyrics as well. I would like to know if it is correct to use (apart from literature context) and what it means and how it is different from "where there are mountains of gold". Thank you!