Davis-urmom wrote: … I want to do this while still keeping all of my metadata intact, dates taken, location, etc.
All that metadata is stored in the Photos Library's database, and the link that muguy shared puts your Photos Library on an external drive. By storing the Library (with the database and not just picture files) locally, you're saving every bit of information that's about those pictures.
Your Mac is a MacAir, so keeping it portable is a different issue-- you don't want to carry the laptop around with a drive dangling from it. One way keep a Library on an external drive and still be portable is to use Optimize Photos storage on the Mac's internal drive, but store the full Library on the external drive as a different user. That way, the normal user won't be plugging an unplugging the drive, which causes some confusion to iCloud communication.
See this:
Backup iCloud Photos with an Optimized Mac