Using Metadata in Flows
Metadata is simply a way of describing optional extra data that may be sent into a flow. You'll commonly find a Metadata output on bot triggers (extra info provided by the bot platform) or Flow triggers & actions (extra info you can provide when triggering another flow or using goto).
The documentation right here on this site will tell you where metadata is provided for bot triggers (check the help doc for the platform the request is coming from). For Flow triggers or actions, you'll provide the metadata yourself (key/value) as an input to the Trigger a Flow or Goto a Label actions.
In any case, you can always see what metadata is available by inspecting the logs. This is the log for a Bot > New File trigger where we're receiving the user's location:
Looking at the above example, to use the metadata key long anywhere in a flow (either on the filter step or in any input field), you simply select it as you would any other output:
Once you've selected the metadata output, you'll then be able to type the metadata key you need. Like this:
Press <enter> when you're done to save the output into the field. If the metadata key long is found, then it will be inserted here when the flow runs.
You don't need to know for sure that metadata is available. Like any other output, if the metadata key doesn't exist, the output will simply be empty.