With automatic metering, the camera is sampling and averaging what it sees in the frame (check your info/instructions for your camera) It tries to match a brightness to neutral (18%) grey, so an all white scene will become dark and underexposed; an all black scene will become lighter and overexposed. The human eye can appreciate so much more variances in lighting and adapt so much more quickly so what you see is not what the camera sees. If you aim for a midway shade/darkness , in the clouds, can help to reduce an under (too dark) or over (too light) exposed photo. You can also set the camera to adjust its light metering, using a piece of cardboard with 18% grey. In this way, the automatic metering will compensate for scenes which are excessively bright or dark. (You should check your camera instructions on how to do this)
Usually, I prefer to use manual metering. That way, I can control and adjust the brightness, making it easier for me to pick a midway tone/brightness and use this. I can meter the light on the area, of the photo, that I want to be exposed more accurately - eg. ambulance - in the composition. I can also use this for keeping an area in silhouette (or almost silhouette), if I wish. Both photos below are straight from the camera and not adjusted in post production.
I have started to shoot in RAW which captures more information (not compressing/reducing to jpg), giving me more room to wiggle later. As I have mentioned, in other posts, I do not usually use computer post production for photos. This is one exception. I am not au fait with photo enhancement programmes. I have only recently started using GIMP for colouring up my artwork and must admit, I only really know how to to basically tweak the contrast and satuaration (how much colour) as I don't own a polarisation filter (which can help to improve contrast in photos where the sky fills the frame, also for bright days which can bleach out contrast).
The first photo above, is straight from the camera with no enhancement. The one on the right (above) has only had some simple contrast adjustment. Both were taken on the same day, at the same location, with just a slight movement in the camera.
It takes practice and I am still only happy with a third to half of my 'sky or cloud' shots, but photography is like that. You very rarely can go back and take the photos again; the lighting has changed or the event has passed.
The moment is ephemeral and fleeting... a bit like life..