"Should" and "would" are two of the 10 modal verbs in English (the others are "can," "could," "may," "might," "must," "ought," "shall," and "will"). ... "Would" is the past tense of the modal verb "will." Used as an auxiliary, "would" expresses a possibility, an intention, a desire, a custom, or a request.

When we use would should and could?

Just remember that could is used to talk about something that can happen, would is used to talk about something that will happen in an imagined situation, and should is used to talk about something that ought to happen or must happen.

Should would could verb?

Would, should and could are three auxiliary verbs that can be defined as past tenses of will, shall, and can; however, you may learn more from seeing sentences using these auxiliaries than from definitions.