Love is a strong word. Demeter, God of Plants, loved her daughter more than anything and her daughter's feelings reciprocated.
All throughout the year, the sun was shining as it was always spring and summer (it was inpossible to catch a glimpse of snow). The plants were always standing upright, in response of their benefacor, Demeter, who always kept them healthy. This world beamed with happiness, in a state of rapture.
Meanwhile in the underworld, everything was in a wrathful state, including Hades. Hades lived in solitude, and craved company, even if it meant it would be forcefully.
No one would expect that these two would end up together, I mean they are polar opposites. But that all changed when Aphrodite felt the need to prove to her son that she could make anybody fall in love. And of course, she just had to use Hades and Persephone as her subjects.
Hades was now madly in love and wanted Persephone as his wife. So, he went to get Zeus, her father''s consent, which he did. But Zeus admonished him that he wouldn't get Demeter's approval.