Sequence is a smart contract wallet, so there's no one "wallet seed" or "recovery phrase" you can import into a wallet like Metamask.
Metamask and many others are "externally owned account" wallets (EOA), but your Sequence wallet is a multisig wallet that requires special code to interact with, so no other wallets support accessing Sequence wallets.
The smart contract wallet will hold users’ assets instead of users having their assets directly accessed by their private key.
One example of this benefit is that the issue of account recovery—a persistent problem for wallets—is solved using this multi-signature design.
Indeed, a Sequence smart wallet can be controlled by multiple keys instead of a single one. This is possible because the assets are held by the smart contract itself; whereas, with traditional wallets, assets are held by a single private key.
We're currently working on a feature to enable users secure one of the private key themselves, without needing to use social accounts login to access their Sequence Wallet.
When using this feature, a backup key will also be generated and users will need to store them securely.
With Sequence, private keys can be added, replaced or removed. This multi-key design, also known as multi-signature, adds security and flexibility, as you need a quorum of keys to perform any transaction with the smart contract wallet.