The example I gave was based on the metering from a bright part of the sky. It's all about the light levels.
Essentially your challenge here is that you have a very high variation in light-levels from brightest to darkest.
The ND Grad Filter can darken the brightest part of the image - in this case the sky - so that the light levels are more even. However, there are are ND filters that go up to 10 stops (or more) of light-dimming. Depending on your scenario, the filter will take you SOME of the way - but perhaps not all.
With a filter, but metering for the brightest part of the sky, may still leave the ground too dark. Playing with the exposure bias - e.g. dialling it a few steps, may bring out the ground to a point where post-processing can do the rest.
The limitation lies in our cameras' ability to span the whole range of light-levels without rendering anything pure white or black. Typical sensors will encompass 7 F-stops in range and the trick is to bring the brightest and darkest areas within that range.
Ideally the LCD should show you what's commonly referred to (warning: very technical term here) as "blinkies", indicating either complete over- or underexposure. However, that is a very rough indication and before blinkies occur you can still hit a threshold that is effectively unworkable. So I would encourage you to evaluate the exposure with your own eyes as well.