I know fields are supported when you put them in the compact layout. But I want to include like a component. Is that possible?
The compact layout is quite limited and you can only insert fields.
There is no other way to modify this region aside from selecting some fields to use. You would need to insert a Visualforce page into the record Detail section at the top of the layout if you want to insert a dynamic message / component that would be seen when the record is opened.