How to buy SOL on MetaMask?

Could you please enlighten me on the process of purchasing SOL tokens through MetaMask? I'm interested in understanding the steps involved from start to finish. Do I need to connect my MetaMask wallet to a specific exchange first? And once connected, how do I navigate the interface to locate and purchase SOL? Also, are there any fees associated with this transaction, and if so, how are they calculated? Additionally, could you provide any advice on how to ensure the safety of my transaction and protect my digital assets? I appreciate your assistance in guiding me through this process.