Seem is a copular verb. It is followed by adjectives, not adverbs.
- He seems angry about something. (NOT He seems angrily about something.)
- She seems depressed.
Seem to be
Seem is often followed by to be. In general, seem to be is preferred when we are talking about things that seem definitely to be true.
- Things far off seem to be small.
- The milk seems to be sterilised.
In many cases both seem and seem to be are possible.
Seem to be is normal before nouns or noun phrases.
- There seems to be some misunderstanding between them.
- I spoke to a man who seemed to be the boss.
- She seems to be a nice girl.
Seem with infinitives
Seem can be followed by the infinitives of other verbs.
- They seem to have made a mistake.
- She seems to need help.
Sometimes it is possible to begin these sentences with a preparatory it.
- It seems that they have made a mistake.
- It seems that she needs help.