When using third-party apps, beware, some of them create their own default wallet, different from a Trezor generated one. (For recovering such wallet you would need a recovery seed related to this wallet which is different from Trezor generated wallet.)
Once you initialize MetaMask wallet, there is a default account created (the red one in the picture) where you have your funds now. If you wish to use it, then you need to keep your MetaMask seed phrase to recover and access this account whenever needed. This account is not a part of Trezor wallet. and those addresses are derived from Metamask recovery seed.
On the contrary, there are Trezor accounts (the yellow and the blue one in the picture). The same accounts are generated in MEW, Trezor Suite etc. These are Trezor generated accounts and can be recovered only by using Trezor recovery seed.
So to sum it up, even if you connect your Trezor to MetaMask, you will still need to transfer your remaining funds from MetaMask standalone account to Trezor one by regular transaction.