Psalm 45 is a marriage song written for the Davidic king. The poem praises his physical beauty and martial prowess. The queen-to-be is also praised and encouraged to take the king's hand. Given all this, I don't think Psalm 45 is in anyone's Top 10 list. The song is too specific to the royal court, and some of its gender assumptions make it fall a bit flat for many modern readers. It's just hard to see yourself in the poem.
And yet, throughout Christian history these songs have been interpreted as describing the wedding of Christ with his church. Israel's covenant with God is routinely described as a marital bond. Revelation describes the New Jerusalem as "the bride of Christ."
Within Protestantism, these marital metaphors remain pretty much metaphors, and thin ones at that. But within the Catholic mystical tradition, the bridal and erotic imagery of Scripture has been used to describe the soul's passion and longing for God. Consider the most famous treatise in the Christian mystical tradition, St. John of the Cross' The Dark Night of the Soul. John of the Cross' discourse is a commentary upon an erotic love poem entitled "Stanzas of the Soul." Here is the poem as translated by David Lewis:
I.
In a dark night,
With anxious love inflamed,
O, happy lot!
Forth unobserved I went,
My house being now at rest.
II.
In darkness and in safety,
By the secret ladder, disguised,
O, happy lot!
In darkness and concealment,
My house being now at rest.
III.
In that happy night,
In secret, seen of none,
Seeing nought myself,
Without other light or guide
Save that which in my heart was burning.
IV.
That light guided me
More surely than the noonday sun
To the place where He was waiting for me,
Whom I knew well,
And where none appeared.
V.
O, guiding night;
O, night more lovely than the dawn;
O, night that hast united
The lover with His beloved,
And changed her into her love.
VI.
On my flowery bosom,
Kept whole for Him alone,
There He reposed and slept;
And I cherished Him, and the waving
Of the cedars fanned Him.
VII.
As His hair floated in the breeze
That from the turret blew,
He struck me on the neck
With His gentle hand,
And all sensation left me.
VIII.
I continued in oblivion lost,
My head was resting on my love;
Lost to all things and myself,
And, amid the lilies forgotten,
Threw all my cares away.
St. John of the Cross uses this poem for the rest of The Dark Night of the Soul to expound upon "the way and manner which
the soul follows upon the road of the union of love with God." The lover goes out into the night for a moonlight tryst with the Beloved. This romantic rendezvous with the Beloved is the regulating metaphor for The Dark Night of the Soul.
And if you're familiar with the bridal and marriage Psalms, like Psalm 45, along with the Song of Songs, all of this imagery is perfectly natural and expected.