The verb "sollen" is a crucial modal verb in the German language, used to express obligation, duty, or necessity. It is equivalent to the English modal verb "should" or "ought to," and is often employed to convey what is expected or required according to rules, social norms, or the speaker's opinion. "Sollen" can also be used to relay hearsay or to suggest what is believed to be true or likely. As a modal verb, "sollen" modifies the main verb in a sentence, shaping the sentence's mood and meaning by indicating a sense of duty or recommendation. Understanding the use and function of "sollen" is essential for mastering the nuances of expressing obligation and expectation in German.