Nikon: Shutter half-press vs AF-L/AE-L button?

Ok, I'm inside a cave and then I want to use the Spot Metering on my Nikon DSLR to make the entrance of the cave bright and the interior of the cave (where I'm) dark. Then, after locking exposure to the cave entrance, I want to recompose and move the cave entrance to the side of the frame.

My question is that, does half-pressing the shutter locks exposure as well as focus just like what holding down the AF-L/AE-L button does?

Normally it does, but various configurations can be setup within the menus on most cameras like AF- Lock only.

Alternatively, meter what you want then dial the aperture and shutter speed in manually. That way there's no need to faff around with buttons.