Some components require metadata on their ports to have a specific structure. For example, see Error Metadata for FlatFileReader. For some other components, such as File Operations, the metadata structure is not required, but recommended. In both cases, it is possible to make use of pre-defined metadata templates.
In order to create a new metadata with the recommended structure, right-click an edge connected to a port which has a template defined, select New metadata from template from the context menu, and then pick a template from the submenu.