Submitting your metadata to large data repositories allows you to leverage their presence and significance on the internet to make your content findable and to promote it beyond your current audience. As well, it can help indicate that you are the authoritative source of your content.
For the purposes of depositing metadata into repositories, metadata is the high-level descriptive information about a dataset that is used in the discovery and identification of data or objects. Metadata may include characteristics of the dataset such as its Title, Creator, and Description, and can help others to understand more about the data and objects, including who created them, where they can be located and what their content is, and whether it may be of use.
Deposit with a repository requires that depositors provide information for metadata fields as defined by the repository. For adding metadata for a single object the process usually involved logging into a repository and filling out an online form with the metadata for the object in question. If you are adding one film or book or other creation this will include fields for the relevant information about that object as well as some location and format information.
For batch uploading often there is a template available and your metadata will need to be adjusted to meet the template structure, then uploaded. If templates and instructions are not readily available just contact the organization or repository in question and ask for help before adding a lot of items individually.
Common repositories are IMDb, Wikidata