Well... yes. You should learn those if You want to improve Your Eng! It'll be usefull when You'll be learning at the intermediate level or higher. A numebr of expressions, tenses, structures etc are described with those notions so knowing them is useful and saves Your time while learning e.g.
conditional clause main clause
present tense future (shall/will + infinitive)
modal verb + infinitive
e.g. If I get some perple wool, I'll make you a pullover.
I can make you a pullover.
will you make me a pullover? (a request)"
example is derived from my grammar book; it's authentic ;)