All modal verbs are auxiliary verbs, which means they can only be used with a main verb. Modal verbs cannot be a main verb. They are used to express ideas such as possibility, prediction, speculation, deduction and necessity.
60+ frases con los verbos más necesarios en Inglés
We've stared at it, howled at it, and composed poems to it…we've even landed on it. Here's a look at the major lunar phases and phenomena— plus a few of the myths it's inspired. http://futurism.com/images/moon-phases-and-phenomena-infographic/?utm_campaign=coschedule&utm_source=pinterest&utm_medium=Futurism&utm_content=Moon%20Phases%20and%20Phenomena%20%5BINFOGRAPHIC%5D