To sell cryptocurrency from your Metamask wallet, you will need to transfer it to a cryptocurrency exchange that supports the cryptocurrency you want to sell.

1. Log in to a cryptocurrency exchange that supports the cryptocurrency you want to sell. Some popular options include Binance, Coinbase, and Kraken.
2. Navigate to the "Deposit" section of the exchange and find the address for the cryptocurrency you want to sell.
3. Open your Metamask wallet and click on the cryptocurrency you want to sell. Click on the "Send" button.
4. Paste the exchange deposit address into the "To" field in Metamask and enter the amount of cryptocurrency you want to send.
5. Wait for the cryptocurrency to be deposited into your exchange account. This may take some time depending on the cryptocurrency and the network congestion.
6. Navigate to the "Sell" or "Trade" section of the exchange and select the cryptocurrency you want to sell. Enter the amount you want to sell and review the transaction details, including fees.
7. Withdraw the funds from the exchange to your bank account or other payment method.

Please note that the specific steps and details may vary depending on the exchange you use and the cryptocurrency you want to sell. Make sure to do your research and follow best practices for keeping your cryptocurrency secure. Also, keep in mind that some exchanges may charge fees for depositing, trading, and withdrawing cryptocurrencies, so it's a good idea to check these details before making the transaction.