postgis - PostgreSQL : finding all lines intersecting with a polygon

I am totally new in the world of GIS but as a student surveyor I am working on a project using postgreSQL and PostGIS.

I have one database with all the roads of my country (lines), and one database with a lot of area's (polygons). And for every polygon, I need to find all the roads (lines) that intersect with it (contain in partially or fully).

I do know the ST_Intersects function, but is this the best function to use ? right now I am trying to make a loop function where I loop all the roads to see if they intersect, but there must be a quicker way..

If anybody could get me started, that would be great!

Thanks