Subjunctive is not very significant in modern English. You might encounter subjunctive in American English or in formal text.

Form of subjunctive

In most of the cases, the subjunctive and indicative forms of the verb are the same. Many times you would not realize whether a verb is used in subjunctive or indicative form. While using subjunctive, "s" is not needed in 3rd person singular and the verb "be" remains "be" for all forms in present tense and becomes "were" for all forms in past tense.

Uses of Subjunctive
Uses of Subjunctive

Subjunctive is used in some certain fixed phrases
  • Long live the king
  • Thy will be done.
  • Be that as it may.
  • God save the queen!

Particular verbs (example: demand, insist, suggest, recommend) and adjectives (example: essential, important, vital) are followed by "that" + subjunctive to suggest that something must be done (directive aspect).
  • People demand that the forces be withdrawn.
  • It is imperative that everyone go.

Sentences in subjunctive sound very formal, that is why often an auxiliary is preferred.
  • People demand that the forces are/ should be withdrawn.
  • It is imperative that everyone goes.

Look at the following sentences:

He insisted that she be present. (He wanted her to be there)
He insisted that she was there. (He knew that she was there)