Problem scenario
You are setting up MetaMask for the first time. It says "First, enter the Secret Recovery Phrase that you were given when you created your wallet."
You read this:
Do not share your recovery seed with anyone else.
https://trezor.io/learn/a/how-to-use-a-recovery-seed
Do not keep digital copies of your recovery seed (this includes screenshots, photographs, emails, Dropbox backup etc).
You read this:
Importing your Trezor seed into a wallet like Metamask will reduce your security to that of a hot wallet, even if you later put the seed on another Trezor.
https://www.reddit.com/r/TREZOR/comments/nbo989/set_up_trezor_recovery_seed_through_metamask/?rdt=46267
Should you enter the Trezor 12 word recovery phrase as prompted to use MetaMask?
Solution
No, usually you should not.
If you have not used MetaMask before, you will be required to set up a wallet and generate a recovery seed. This recovery seed is separate and is not part of your Trezor and is not necessary if you only intend to use MetaMask with your Trezor.
https://trezor.io/learn/a/metamask-and-trezor
Do not import an existing wallet. Start over and create a new wallet for MetaMask.
If you already sent a coin to a Trezor address and that coin is not supported by Trezor natively, you may need to import your recovery seed into MetaMask to use the coin; in fact, after you do the import, you may need to import a modicum of a subsequent coin of that type of cryptocurrency to the address again to see the total balance in MetaMask. The subsequent coin could have only a nominal value, but that may be necessary. If you have not sent any coins that are not natively supported by the wallet, and you do not intend on using coins not supported by the wallet, to be secure, we do not recommend you import your wallet or give your recovery seed to another entity/party or software application (such as MetaMask).