If you have ETH or other tokens that you want to exchange for fiat currency, you will have to do so on an exchange, as MetaMask does not provide this service. This means sending the tokens manually to the exchange platform of your choice.
When you do so, please bear in mind:
- You will need some of network's native tokens in order to pay gas fees for the transaction of sending the tokens. This could be ETH for Ethereum mainnet, for example, or BNB or MATIC for BNB Smart Chain or Polygon respectively.
- You need to ensure the exchange supports the network and tokens you're using. For example, if you're sending MATIC, make sure the exchange supports the type of MATIC you're using (ERC-20 or native). You should not send native MATIC (on Polygon itself) to an exchange that only supports the ERC-20 MATIC, as you'll most likely lose the tokens forever. Be sure to check the exchange's support documentation to verify which network you should send on.
For details on how to send tokens from MetaMask, please check our article on sending tokens out of MetaMask.