How do I buy Aptos with Metamask?

Could you please explain the process of purchasing Aptos using Metamask? I'm quite new to the cryptocurrency scene and am trying to understand the steps involved. Do I need to have a certain amount of Ethereum in my Metamask wallet before I can proceed? Also, how do I ensure that the transaction is secure and the tokens are legitimately purchased? Would it be advisable to conduct some research on the current market price of Aptos before making the purchase? And finally, are there any additional fees or charges that I should be aware of when using Metamask for this transaction? Thank you for your assistance in guiding me through this process.