Normal map issue

[Henriquebg88]

Why isn't my normal map working? 

When i apply it, i can see through the model (wtf?)

There is nothing wrong with it... 

[Henriquebg88]

And suddenly it worked... 

[OptimoMaximo]

Set the alpha mode as None and this effect will be gone.

As a side note, it's best to set the background to a neutral normal value instead of black, even if you set the padding as you did. The value is very easy to remember, most precise if you use a 0-255 RGB encoding: R=127 G=127 B=255