Will Nikkor AF-D lenses fit on a G-mount?

I've been looking everywhere for the answer to this, someone please help me out here

There's no D or G mount, all Nikon SLR/DSLR bodies use the Nikon F mount. D and G and AF and AF-S and VR and whatever else they add on are features of the lens, not the mount. D means "distance integration", G means no aperture ring. They all use the same bayonet to attach the lens to the camera.

Yes, your problem comes with the D3000/D5000 series and other budget models;

They WILL fit.

They WILL allow all metering modes.

They WON'T autofocus.

Virtually all modern Nikon SLRs and DSLRs (made in the last 20 years) can use D lenses, while all G lenses work with virtually all DSLRs. D and G lenses have minor differences, but one difference is the autofocus motor.

Most AF mount lenses are also D mount (with the exception of the Nikon AF 10.5mm DX fisheye) which is a G mount.

If you have a modern DSLR, D or G lenses will work 100%. However, more importantly is if you have an entry level DSLR (D3xxx, D5xxx, D40, D60), they will only autofocus on AF-S lenses. Since most D lenses are also AF, which will not autofocus on entry level DSLRs, this is a consideration if you have one of those cameras.

So in summary:

AF-S "G" lenses will work 100% with every Nikon DSLR ever made.

AF "D" lenses will work with all Nikon DSLRs as well as many film SLR cameras, although they will not autofocus on entry level DSLRs.

AF "G" lenses (of which I'm aware of 1 lens - the 10.5mm Dx fisheye) will work with DSLRs but will not autofocus on entry level DSLRs.

G is not a type of mount.