The subjunctive idea is sometimes expressed by verb phrases, containing the auxiliary verbs may (might), would, or should. May, would, and should are not, however, always subjunctive. In "I may go" (may = am allowed to), may is indicative. In "you should go" (= ought to), should is indicative.
The subjunctive mode is used most frequently to express:—
1. A wish: [The Lord be with you].
2. A condition regarded as doubtful: [If it be true, what shall we think?], or a condition regarded as untrue: [If I were you, I should go]. When condition is expressed by the subjunctive without if, the verb precedes the subject: [Were my brother here, he could go with me].
3. A purpose: [He studies that he may learn].
4. Exhortations: [Sing we the song of freedom].
5. A concession,—supposed, not given as a fact: [Though he be my enemy, I shall pity him].
6. A possibility: [We fear lest he be too late].
The tenses of the subjunctive require especial notice. In conditional clauses, the present refers either to present or future time: [Though the earth be removed, we shall not fear].
The preterite refers to present time. It implies that the supposed case is not a fact: [If he were here, I should be much pleased].