its a comparison to how much a person can love another. The love is like an addiction, and it becomes necessary to that person.
"Dope fiend, dope fiend
I'm just like a dope fiend
When it comes to your love
Girl I'm like a junky
Dedicated to your drug
Baby let me get some
Smoke you, snort you, shoot you in my system"
Im so addicted to your love, im like a dope fiend for you.