What is love? Socrates felt Divinly inspired:
"Every one sees that love is a desire, and we know also that non-lovers desire the beautiful and good. Now in what way is the lover to be distinguished from the non-lover? Let us note that in every one of us there are two guiding and ruling principles which lead us whither they will; one is the natural desire of pleasure, the other is an acquired opinion which aspires after the best; and these two are sometimes in harmony and then again at war, and sometimes the one, sometimes the other conquers. When opinion by the help of reason leads us to the best, the conquering principle is called temperance; but when desire, which is devoid of reason, rules in us and drags us to pleasure, that power of misrule is called excess. Now excess has many names, and many members, and many forms, and any of these forms when very marked gives a name, neither honourable nor creditable, to the bearer of the name. The desire of eating, for example, which gets the better of the higher reason and the other desires, is called gluttony, and he who is possessed by it is called a glutton-I the tyrannical desire of drink, which inclines the possessor of the desire to drink, has a name which is only too obvious, and there can be as little doubt by what name any other appetite of the same family would be called;-it will be the name of that which happens to be eluminant. And now I think that you will perceive the drift of my discourse; but as every spoken word is in a manner plainer than the unspoken, I had better say further that the irrational desire which overcomes the tendency of opinion towards right, and is led away to the enjoyment of beauty, and especially of personal beauty, by the desires which are her own kindred-that supreme desire, I say, which by leading conquers and by the force of passion is reinforced, from this very force, receiving a name, is called love." Phaedrus
Love, according to Plato here, is a force and I agree with that. For Plato that force is the result of the conflict between reason and desire. Love has its roots in our primal species desire, to reproduce. That primal desire is played out in society's concept of the correct forms of physical engagement.
I think love can be a form of narcissism where the lover loves the beloved because they see in the beloved them self. The desire for the beloved here is the imaginary love of ones's self, in spite of differences. The lover's desire is for the beloved to reciprocate, to desire the lover. The lover's impossible desire is to be whole, this is the excess that love adds to a relationship, which is beyond the basic force of sex, and it is rarely obtainable.