Love in The Merchant of Venice comes in a variety of forms. There's love between family members, between friends, and of course, between lovers. Still, love is more notable for its absence than its presence in the play. Love often goes hand in hand with betrayal. Bassanio says he "loves" Portia, but he courts her for her money. At times, the same seems true of Lorenzo's interest in Jessica. Women seem happy to give love, but they do so with a shred of cynicism. Antonio clearly loves Bassanio (whether romantically or not), but he ultimately must subordinate this love to Portia's more formal marriage with him. Love is regulated, sacrificed, betrayed, and generally built on rocky foundations in the play.
Portia does not love Bassanio. Based on her citing the Hercules myth, we know she knows he was using her to get to her money. Because she's a practical woman, she's convinced herself to care for him anyway. She's making the best of a bad situation, which is why she's willing and interested in asserting her power over him at the end of the play.
Even though he is too gruff to express it, Shylock truly loves his daughter Jessica. When she deserts him, leaving him entirely alone in the world, he is transformed from a mildly grumpy man into an actively malicious one.