Love is reflection. Borrowing liberally from Hamza Yusuf's lecture at RIS, when you're in love with someone, you mimic them. You try to be like them. If your Layla's Egyptian, you'll learn Arabic for her. You'll adopt a different culture for her. You basically just copy them.
If love were to be put in equations, they'd probably fall somewhere in the field of Optics under Physics.
A metaphor for love: Your heart is a mirror. Nobody will have trouble accepting this, as that's been in Sufi tradition for over a thousand years. Everyone's born with a mirror, which is the source of their ability to love and other spiritual things. (It's called a 'Qalb' in Arabic).
You point that mirror at things you love, and reflect them within yourself.
Biological love can also be explained in this metaphor. If you're reflecting something, you're kind of loving it. You are born reflecting your parents, because you have their DNA. You love them because they reflect you. They love you because you reflect them.
I'm pretty sure if we started cloning ourselves, you would have a kind of love for your clone and vice-versa. Maybe a strange kind of love, but something that qualifies as love nonetheless.
As Sufis say, when you love God, you reflect His Divine Attributes. That is the goal of all spiritual enlightenment.
When you love other people, you point the mirror at them. But this is blinding. They'll probably be like "wtf, get that thing out of my eye" and point their mirror back at you, which will blind you. Two people pointing their mirrors at each other cannot keep the mirrors focused on each other because they'll lose sight of each other and wind up reflecting nothing. This is a metaphor for 'romantic' relationships of the day. The best compromise is to point the mirror at the other person, then lower yours and have them point their mirror at you. Just like how in relationships, it is usually one party in love with the other at any given moment, and then they swap. One gets used to having the other, takes them for granted, and falls 'out' of intense feeling while the other will suddenly fall into it. Laws of human attraction, it's a game of attention.
Needless to say, such a thing cannot really be love between people. That is the problem with attraction. Everyone has love, but that's not how you connect it to another. There's also the fact that love is only of as high a quality as the lover, not the beloved. (That the lover reflects the beloved later is a different factor). So the highest form of love would be for the sake of God. (Not for anyone's sake, not for love's sake, not for goodness' sake, but literally for the sake of God... and loving something for the sake of God is the border land between Faith and Love which are different phases of the same thing).
"Love is not looking at each other, but looking out at the world together."
A better balance than to shine shit into each other's eyes and make each other blind and ultimately frustrated, angry, and very much NOT in love would be to hold your mirrors together and reflect the rest of the world. And God. This is the highest form of love between people, and it just so happens to not be limited to romantic love at all. In fact, it might even exclude the contemporary idea of romantic love. This is something more akin to a type of friendship, or more aptly put, 'companionship'... although spouses are set up in optimal circumstances to become best friends or true companions within Islamic culture dictated by Islamic law. For instance, incredible love exists between Spiritual master and apprentice (sounds almost Star Wars...). A Shaykh and his Mureed. A huge chunk of Rumi's works were him going crazy over his Shaykh: (Wikipedia: As the years passed, Rumi attributed more and more of his own poetry to Shams as a sign of love for his departed friend and master. Indeed, it quickly becomes clear in reading Rumi that Shams was elevated to a symbol of God's love for mankind, and that Shams was a sun ("Shams" is Arabic for "sun") shining the Light of God on Rumi.)
Back to the love between man/woman, which has the natural advantage to reach the highest stage of love above all other types of human relationships (even above parent-child). What are children, if not the perfect expression of love? The two reflect themselves into one new mirror. You don't carve the likeness of your beloved into a mountain. Mountains end. But into a new human being, combining half of your two signatures is the most perfect way. And in fact, the very act of having children itself is as if the two pointed their mirrors together at Allah Himself. The birth of a child is reflection of the Divine Attribute of Creator which cannot be reflected by humans in any other way (save extraordinary Prophets with the gift of miracles). This is why the vision of God in woman is the most perfect of all because she is literally a mirror for the act of Creation.
The fact mankind continues to exist, is due to Allah's love for it. Simply reproducing and achieving it's nature is a touch of His Mercy and Love since life itself reflects the most basic ideas or Divine Attributes of 'God's image'.
I should also mention most people completely dirty up their mirrors by our age (young adults). So it doesn't work exactly like it should. Spiritual exercise (expressing faith in practice) is like rubbing. It wipes it clean. Although if you go too far (some crazy ascetics), you could end up warping the mirror but I doubt any of us will ever get that far in this world. The Qalb is also a source of thinking and intelligence according to Islamic philosophy. Except it recieves knowledge from Divine Insight and Inspiration, so a functioning Qalb will only give you Truth and an understanding of the true nature of things. The problem is when amateurs can't tell whether they're listening to their Qalb, to their Nafs (al-Ammara), to Shaitan, or to other people.