Neither of your sentences is in the imperative mood, examples of which are 'Go away!' and 'Bring it here!' the subject (you) being omitted.
'Here comes the bus' is a simple statement, 'the bus' being the subject.
'Sweet are the uses of adversity' is an inversion of 'The uses of adversity are sweet', the subject being '(The) uses (of adversity)'.
I can't figure out the meaning, either.
Student or Learner