How do I buy crypto currency in MetaMask?

Inquiring minds want to know, could you provide a concise step-by-step guidance on purchasing crypto currency through MetaMask? I'm new to this platform and am seeking clarity on the process. Specifically, I'd like to understand how to fund my MetaMask wallet, choose a cryptocurrency to purchase, execute the transaction securely, and ensure the funds are safely stored within the wallet. Additionally, are there any specific fees or considerations I should be aware of before initiating a purchase? Your expertise in this field would be greatly appreciated.