1. They looked like they WERE having a wonderful time. 2. They looked to be having a wonderful time. They have about the same meaning, but (1) sounds more colloquial. it is what most people say in daily situations. (2) sounds a bit formal and serious, and "They appeared/seemed to be..." is more common than "looked to be", although "looked to be" is certainly not wrong. There are also these related structures: - It looked like they were having a wonderful time. - It appeared that/like they were having a wonderful time. - It seemed that/like they were having a wonderful time. All these sentences mean more or less the same thing, with only a very small difference in nuance.

Thank again, Michael!

Yes :)

Thank you, Michael! They looked to be enjoying the concert. Is it also correct?

Yes, very similar. The first one should really have a "were" instead of an "are", though. They looked like they were having a wonderful time.