more|more Idiom
the more|more
-- the more ---|the ---er the ---er

Used in two halves of a sentence to show that when there is more of the first, there is more of the second too.
The more you eat. the fatter you will get. Get your report in when you can; the sooner, the better. The bigger they are, the harder they fall. The more Bill worked on the arithmetic problem, the more confused he became.
the more the merrier|merrier|more|more the merrier
n. phr. The more people who join in the fun, the better it will be.

Used in welcoming more people to join others in some pleasant activity.
Come with us on the boat ride; the more the merrier.