"My True Love Hath My Heart" by Sir Philip Sidney is a metaphor. Explain the poem and its significance.

"My True Love Hath My Heart" by Philip Sidney uses the
literary device of metonymy. Metonymy is when someone writes about something, but does
not use its name to describe it—instead he/she uses something
associated with it.

For example, when
we say we could eat the whole plate (of cake), we are not referring to eating a plate,
but the food on it.

For this poem, the
metaphor I find is that the heart represents love. The
metaphor is that the heart is said it is "given" like a tangible item, when it really
refers to sharing an emotion, something intangible.

Each
lover has shared his/her heart (love) with the other, and the other, in turn, has done
the same. "He loves my heart for once it was his own." So the two have shared their love
for one another. In doing so, the love has altered, become something new in combining
the two separate loves into one.

The exchange of love,
represented by the heart, is shared between these two, but it's hard to tell where one
person's heart stops and the other person's heart begins. They become like two hearts in
the same chest.

The best way for me to make sense of this
is to suggest that when one gives his/her heart to the other, they become inseparable:
not physically, but metaphysically. The essence of one joins with
the essence of the other and they cannot be distinguished from each other any
longer.

When Elizabethan's married they believed that at
that moment, they were inseparable forever. This is why in Hamlet,
by William Shakespeare, Hamlet's mother is committing incest by marrying her
brother-in-law: for within Gertrude there still resides a part of her dead husband (Old
Hamlet)...therefore, Old Hamlet is sleeping with his brother (Claudius) when
Gertrude sleeps with
Claudius.

As Sidney lived at the same time as
Shakespeare—during the Elizabethan period—I believe he would also have been influenced
by Elizabethan perceptions: it makes sense to find this kind of "imagery" is used in
Sidney's poem.

The idea of oneness guarantees that each
person will do all he/she can to make the other happy, for each has a part of the
other's heart, the other's love. And hurting the other would, in fact, hurt
him-/herself.

Like a house of mirrors—it is a little hard
to follow. Hope this helps.