How to buy tokens on MetaMask?

Could you please explain the step-by-step process for purchasing tokens on MetaMask? I'm new to the platform and would appreciate a detailed guide on how to navigate through the process. What kind of wallet do I need to set up first? Do I need to have Ethereum or any other cryptocurrency to purchase tokens? Are there any specific fees associated with buying tokens on MetaMask? Lastly, how can I ensure the security of my tokens once they're purchased? Thank you for your assistance.