How do I fill a gap between the ceiling and wall (drywall)?
A small spot of damage is best filled with drywall compound and I like to use fibabfuse tape….a patch. Or as others say, painters caulk will also fill a small gap and paint up nicely. Or spackle. If you have an entire wall, then a pro would tape and float the joint. Caulk is not the best solution for an entire wall, but it will work. Be sure to use a damp kitchen sponge with rounded edges to smooth the joint and clean the caulk off everywhere but the gap. Caulk will have a different look than a taped and floated joint, but it will look reasonably okay if tidy, possibly better than an inexpertly floated seam (although drywall mud is easily sanded smooth).