Does it cost money to use MetaMask?

Excuse me, could you clarify something for me? I've been hearing a lot about MetaMask lately, and I'm interested in trying it out. But before I do, I wanted to know if there's any cost associated with using MetaMask? Is it a free service, or do users have to pay some sort of fee to access its functionality? I'm just trying to make sure I understand the financial implications of using MetaMask before I dive in. Thank you for your help!