Verbs(action verbs) have to be conjugated to be used in sentence. Adjectives(state verbs) can be used without conjugation for the present tense. For more information, refer to http://www.italki.com/question/265810

All sentences must have at least one cojugated verb, however there can be additional verbs that are not conjugated, depending on their function in the sentence. Feel free to provide an example of a sentence that you are wondering about.