When editing a Content Type, the "Metadata" option is not available in the dropdown list (see screenshot).

According to the settings of eZ Platform, this option should be available by default.
https://github.com/ezsystems/ezpublish-kernel/blob/master/eZ/Bundle/EzPublishCoreBundle/Resources/config/default_settings.yml#L89

The translation for this category has not been generated
https://github.com/ezsystems/repository-forms/blob/4ea89125ff7079131dd6f2d1fd8571e1d2a27a63/bundle/Resources/translations/ezplatform_fields_groups.en.xlf