How to purchase ETH on MetaMask?

Could you please elaborate on the steps involved in purchasing Ethereum (ETH) using MetaMask? As a crypto enthusiast, I'm keen on understanding the process thoroughly. Specifically, I'm interested in knowing if there are any prerequisites I need to fulfill before initiating the purchase, such as setting up a wallet or connecting to an exchange. Additionally, I'd like to know about the payment options available, including fiat currencies and other cryptocurrencies. Moreover, are there any fees or charges involved in the purchase process, and if so, how do they impact the final cost? I appreciate your guidance in this matter.