Noun clauses are usually introduced by "that, who, what, whom, where, how, why, whether or not, whatever, whichever,..."
A) We use a noun clause as the subject of a sentence.
*** What bothers me is his selfishness.
*** Whether he is rich or poor doesn 't matter.
*** That I study hard is my best habit. (My studying hard)
B) We use noun clause as the object of a sentence.
*** We have to do whatever we can.
*** I’ll be wherever you are.
*** Samuel thinks that he is the handsomest.
*** It is not definite yet -whether he 'II be spending his holiday here or not.
C) We use noun clause as the complement of a verb.
*** My idea is that we should tell him the truth.
*** My attitude towards him was that I tried to be helpful.
D) Noun clauses with "-ever words" :
We can use "-ever words" such as whoever, wherever, however, whatever, etc. in noun clauses. "Whoever" means "anyone who ... "
*** Whoever wants to pass the exam should work harder.
*** You can see whichever film you like.