Question

What is the metaphor is this poem ?

Helen, thy beauty is to me
Like those Nicean barks of yore,
That gently, o'er a perfumed sea,
The weary, way-worn wanderer bore
To his own native shore.

On desperate seas long wont to roam,
Thy hyacinth hair, thy classic face,
Thy Naiad airs have brought me home
To the glory that was Greece
And the grandeur that was Rome.

Lo! in yon brilliant window-niche
How statue-like I see thee stand,
The agate lamp within thy hand!
Ah, Psyche, from the regions which
Are Holy Land!