Future perfect
Relatively rare in English, the future perfect serves to express one future action which precedes a future moment or another future action. Moreover, it asserts that these actions will be completed before the principal action. It is formed by adding the modal "will" to the auxiliary "have," preceding the past participle:
One can often use the simple future instead of the future perfect, but a nuance is lost: the simple future does not emphasize the completion of the first action: