Is it possible to use hard drives as memory storages for my MacBook Air?

Thanks for the A2A.

Nope. At least not exactly.

Computer storage doesn’t work the way storage does in an iPhone. Think of it this way: storage is for the stuff you are not using and RAM is for the stuff you are using.

Now that having been said, your macOS already uses some of the storage space on your computer. This is called Virtual Memory and the way it works is when you fill up the RAM on your computer and then ask it to do something else, macOS takes some of what you aren’t using at the moment and puts it in a swap file where it sits until its needed again. When you switch to the app that uses the data in the swap file, data from another program you aren’t using is swapped out of RAM for the data in the swap file the app you are using now needs. (Thus the name swap file.)

So while you don’t have any control over the process, your computer actually does kind of use some of the storage on the hard drive or SSD as memory already.