The Faerie Queene is his major contribution to English poetry. It is mostly a poem seeking (successfully) the favour of Queen Elizabeth I. The poem is a long allegory of Christian belief, tied into England's mythology of King Arthur. In form, the poem is an epic, in the style of Beowulf and the verses of Virgil and Homer.
The language is purposely antique. As such, it is supposed to remind readers of such earlier works as those mentioned above, as well as the Canterbury Tales of Geoffrey Chaucer, whom Spenser greatly admired.
Spenser's Epithalamion is the most admired of its type in the English language. It was written on the occasion of his wedding to his young bride, Elizabeth Boyle.
Spenser's effort to match the epic proportions of the Aeneid earned his place in English literature. For The Faerie Queene, Spenser devised a verse form that has come to be known as the "Spenserian stanza."
Faerie Queene. Book iii. Canto xi. St. 54.
And as she lookt about, she did behold, How over that same dore was likewise writ, Be bold, be bold, and every where Be bold, That much she muz'd, yet could not construe it By any ridling skill, or commune wit. At last she spyde at that roomes upper end, Another yron dore, on which was writ, Be not too bold; whereto though she did bend Her earnest mind, yet wist not what it might intend.