Plan the metadata change
List the exact keys and values to update and preserve content headers or custom fields that must remain. Check whether the operation replaces all metadata or merges selected fields; assuming merge behavior can accidentally remove values.
For bulk work, test one object and compare content checksum, size, tags, and metadata before and after. Consider retention locks, legal holds, encryption settings, and object versioning, since a rewrite may create a new version or be disallowed.
Apply and verify carefully
Use a narrowly scoped selection and retain a record of object keys and versions changed. Ensure the identity performing the operation has only the needed read and write permissions.
Read back representative objects and confirm both metadata and content remain as intended. If the operation creates versions, document cleanup separately rather than deleting historical versions as part of an unverified metadata update.