Isnt spot metering an important part of the process in order to get this effect?
Not really. You can walk up close to the subject and take what is called a "close-up meter reading" using center-weighted, or even Matrix or Evaluative metering modes, and get a pretty good exposure. You can also point the camera down, so that no sky is picked up, and use that reading. If you have a long telephoto, you can use its narrow angle of view to in effect, do a close-up meter reading from the shooting position.
The thing is: when shooting against the light, there are any number of ways to expose. When in spot metering mode, the exposures tend to vary WILDLY,and I mean WILDLY, based on how much sunlight or flare there is included in the meter's angle of view, or how much light is NOT in the view. Spot metering could lead you quite astray, either OVER- or UNDER-exposing,drastically, depending on the exact, precise aiming of the camera.
What you need to do is to figure out "what the right exposure is". If you have a modern Nikon with a 3-D, RGB Color Matrix light metering system, it is going to give you a pretty good meter reading most of the time. If you have a camera that is color-blind, and which has no idea of either color temperature of the light, nor the colors of the subject, its meter readings are going to need to be interpreted. Spot metering was not an option for many decades, and it causes more screw-ups than fix-ups unless it is used properly. You would never want to use spot metering and then let the camera determine a new exposure for each shot...the exposures will yo-yo all over the map. You need to figure out what "the right" exposure is for the look you want, set that exposure, and shoot your sequences with the same exposure, and re-evaluate the exposure every few minutes as the sun rises or sets. If you are using a FLASH for fill-light or as the main light, then you can adjust the shutter speed for brighter or darker background effects. If you want a semi-silhouette exposure, your exposures would be less, or briefer, than if you want a brighter, more back-lighted, blown-out,dreamy look.
The reason I do not like SPOT metering in this situation is it doesn't tend to include enough of the sunlight. The correct exposure needs to have some reference to the amount of sun- or sky-light that there is on the scene. Plus, the shadowed or dark side of the subject also needs to be included in the metering. SPOT metering in this type of situation is just hair-trigger. I've found that Nikon's center weighted metering does a good job by aiming the central 12mm circle scribed in the viewfinder at the main subject, and using that as a baseline, and then adding or subtracting exposure from that baseline, as needed.