MetaMask includes tools to help you exchange between multiple currencies, including Ethereum, Matic (Polygon), Solana, Bitcoin and more.
Under the hood, this exchange is powered by UniSwap, a decentralized finance protocol that is used to exchange cryptocurrencies.
You'll pay a small fee for processing the transaction, however it's much simpler than opening an account with an exchange and the fee is likely to be much lower than the exchange fees to transfer, exchange and withdraw.
First, open MetaMask and select the currency you want to exchange from. Note that this can only be done for cryptocurrency to cryptocurrency exchanges, you can't convert fiat (USD, GBP etc) - if you're looking for that you'll need to set up an exchange account.
Next, select Swap. In the window that opens, select the currency you want to exchange from, and the currency to exchange to. You can leave slippage as the default, but advanced users may want to tweak this to get the best exchange rate.
For this post, I'll be swapping from Ethereum to MATIC.
Click Review Swap, and check you're happy with the fees. You might see a screen saying "No quote available". If this happens, try increasing the amount to swap or waiting a few minutes and trying again.
As you can see, the gas fee here is pretty high for the total transaction size. It's likely that at the time of writing the Ethereum network was heavily loaded, so it's worth waiting a bit for gas prices to fall.
The gas fee is similar regardless of the amount swapped, so it's much better to wait and swap the most you'll need at once rather than swapping as you need it.
If you're happy with the fees and ready to exchange, click Swap and you'll see your shiny new tokens in your wallet once the transaction is confirmed.