Hi @snacker00
Welcome to the Auth0 Community.
Yes it is possible to update metadata via Lock using additionalSignUpFields as per this example https://auth0.com/docs/libraries/lock/lock-configuration#text-fields
However, the metadata update will not show in the log as a separate item, you will only see it under the Success Signup (type: ss) under Raw Data i.e. amongst the data that was posted as part of the user creation process.
Warm regards.