Is love the subject here? I don't understand it because of verb to be.
Yes it is. Love is the subject: the same when you say "give love" or "all you need is love". Many feelings have this double quality of being an abstract thing and the action of expressing the feeling.
The simple answer to your question is, "yes."
In any simple "to be" sentence, the subject is always to the left of "to be."
I will go. (subject: I)
You are wonderful! (subject: you)
That is amazing! (subject: that)
It was over there. (subject: it)
Only when you get to more complex sentences will you find the subject to the right. Questions are good examples:
How is that possible? (subject: that)
Where has the time gone? (subject: time)
Who was that man? (subject: man)