I am renovating my basement and there is currently a suspended ceiling. After removing some of the tiles I noticed there are some junction boxes without covers. I want to replace the suspended ceiling with drywall. Do I have to cover up the boxes? Or should I be doing this all differently?
Nope on "covering-up", but Yep to put the original or new covers on them.
Junction boxes & any other electrical boxes have to remain accessible & so do all plumbing valves. Home Improvement places have access doors, panels & covers for all sizes of holes you'll need to leave in the drywall.
Yes, you should install covers on the boxes.
You should be able to pick up covers at the local hardware or big box, fairly cheap. Just make sure you measure all the boxes, and note their shape, before heading to the store. If the mounting screws are not in the boxes, you'll also have to pick up some of those.
No, you cannot cover the boxes with drywall. The boxes must remain accessible.