Can I connect any external monitor to an MacAir?

The support article you came here from should provide you with the steps needed to connect an external display to a Mac. Have you reviewed it yet? If you did, and it didn't help, you will need to be a bit more specific on:

• Which exact model is your MacBook Air.
• What version of macOS it is running.
• The make & model of the external monitor ... or, at least, tell us what type(s) of video port(s) it has.
• What you have tried, so far yourself, to resolve any issues using this monitor with your notebook.