Whenever I see a sentence with a restrictive clause or phrase (mainly those with the word "that"), I worry if I need to put the article "the" this time or not. Do you have any good suggestions that will help me to see clearly?


(I think the sentence below can accommodate "the," although it may not be necessary.)

They name (the???) things that have great importance.

Sorry if my question is too broad or not clear.
Want to be specific, say that these are CERTAIN things? You need the.
IMO, the same rules govern this part of grammar as that of articles.
 Marius Hancu's reply was promoted to an answer.