The Verb 'To Be' - Guide to Grammar
guidetogrammar.org/grammar/to_be.htmThe Forms of “To Be” The Greek sea god, Proteus, was (like the sea) capable of changing form in an instant. In order to get any decent information out of him, you had to grab him and hold on tight while he went through his various forms — lion, wild boar, snake, tree, running stream — …
The verb "to be" - main verb auxiliary or modal
linguapress.com › grammar › to-beThe verb to be is occasionally used as a modal auxiliary; but in this it is a strange verb, as it can have either a value of futurity, or a value of obligation, or something between the two, supposition. In the first and third persons, it is a modal whose most common value is futurity: in the second person, its main value is one of obligation.