Can I apply permissions to assets and metadata fields?

As far as i know, there is only folder based permissions.
In the DAM i administered before it was as you described.
We had the option to give user groups the right to see and download assets, based of an VDB value.
One one hand, this was very good to have as an option, on the other it was a horror to micro manage.
Usually the regions and departments knew better what asset was meant for them then the people that had to do the micro management of assets. And as long as they could not see a misfiled asset, they did not know of its existence and had no chance to see the error.
In the AEM we currently use different metadata properties to give departments and regions the option to filter out and find easily what they are looking for + some extra folders that contain assets that are strictly for one region only. The structure had to be adapted.
If by chance this tread finds a way to make it possible to have a user group to see only assets with metadata X and another group to see assets with metadata Y - i would be very interested to hear about it.
I am not that unhappy with the way we changed this setting.

I just thought about something that feels like an solution but i am very uncertain about it...
and do not know if this is an idea worth of pursuit. 

Have you looked into the search rails "hidden predicate"?
 
Maybe you could... create different search search rails...
depending on user group... and then use the hidden predicate to include/exclude assets (based of the metadata property of your choosing) to make the assets visible/invisible?

@dmescia2 Did you find the suggestion from @adilos-cantuerk helpful? Please let us know if more information is required. Otherwise, please mark the answer as correct for posterity. If you have found out solution yourself, please share it with the community.

i think this is possible via customisation, applying permissions to user based on metadata. but we need to write custom logic.

We just met with Adobe engineers who mentioned a feature in beta that will allow us to apply permissions to assets based on the metadata. We'll be testing this out over the coming weeks to ensure it meets our use case. I'll report back with the results.