This is the 5240th most frequent Korean word.
담을
"담을" means "wall" or "fence" (as an object to block or enclose).
In this sentence, "담을" is used as the future or unreal conditional conjunctive form of the verb "담다," which means "to contain or hold." It indicates the action of fitting or being held within a certain space.
핸드폰은 못 담을 만큼 기껏해야 여기에 들어갑니다.
A phone will barely fit here, as this is the maximum size.
Here, "담을" functions as a modifier of the noun "액자" (frame), meaning a frame that will contain. It anticipates the action of enclosing the picture.
그림을 담을 액자가 필요해요.
I need a frame to hold the picture.
The phrase "담을 내용을" implies the materials intended to be included. "담을" here denotes what is to be contained, modifying "내용" (content).