Will my Nikon AF-S NIKKOR 85mm f/1.8G Lens work manually with the Nikon FM3A?

I want to buy a Nikon FM3A, I already own a few very recent lenses and I don't know if they will mount? I understand that autofocus and metering won't work but will I be able to take pictures?

It will mount but the picture it will produce with the film camera will be small and will have large, dark, fuzzy and ugly borders. Then again how would you find a way to control aperture on a G lens that doesn't have an aperture ring? The FM3a I presume is fully manual?

The 85mm f/1.8G is a full frame lens so you will not get any vignetting around the border of the photo.

But it since it is a "G" lens, there's no way to control the aperture of the lens - so you may have a tough time in dialing in the desired aperture (background blur, etc).

But the lens will mount, and you will be able to take a photo.

Metering will work - at the minimum aperture with no way to change it.

Yes and no. Your AF-S 85mm f/1.8G lens will mount on the FM3A and meter but since its a "G" lens and has no manual aperture ring there will be no way for you to select an aperture setting. You'll quickly find this far too limiting to be of any use.