The "guy" starts by comparing the rain drops with tears suggesting sadness. Sadness caused by the fact that he is alone ("I never had no neighbours no"), or at least that is what he feels like ("at least none that I know") because he didnt have anyone special.
In the chorus he is asking why should he let someone close to him, to his soul, because he was alone untill then and he will be after that person leaves...he is afraid of geting hurt.
He continues by comparing his soul to a garden that has a wall of trees to keep everyone out...although he catches a glimpse of what is going on beyond it ("Though you can hear the birds a singin', carried on the breeze"), and although he can feel what's on the other side he was always alone.
He then realises that the person aproaching him is a wolf in sheep's clothing, and that person could be dngerous ("What great shiny teeth you have") and everything is telling him not to trust, not to open up.
I see two possible interpretation for the final verse :
1.That person wants to control and consume him...to use him and to break him from the inside causing him never to want somebody close to him ever again ("I'll never need no neighbours no")
2.That person wants him entirely, body and soul, wants to get inside and be togeather forever ...a very passionate description of love... and then he won't need anyone else ("I'll never need no neighbours no")
Either way...he is never sure of what he wants("at least none that I know")...these are just feelings and they can play many tricks on our rational minds, turning our whole existence upside down.
This is just my interpretation of the lyrics and I dont assume to be 100% right.