The common everyday meaning: a lockable container or room for storing money, valuables, or important documents.
I put the bankbook and seal in the safe.
There is a large vault in the basement of the bank.
treasury; cash office; depository
Institutional or administrative use for a place, office, or organization that receives, keeps, and pays out money. It is also common inside financial-institution names such as 信用金庫.
In the old regulations, 金庫 refers to the department that handles the receipt, payment, and custody of cash.
I consulted about a home loan at a local credit union.
financial backer; source of funds
Metaphorical and relatively uncommon: a person or group treated as the purse or funding source for an organization, party, or activity.
The businessman was seen as the campaign's source of funds.
He opened the safe and took out the cash.
I keep my money deposited at a credit union.
I put the important documents away in the safe.
I lost the key to the safe.