How to simulate deep darkenss or complete darkness?

I'm using Unity 5.01f1 Personal...

I have a scene in which I want to simulate different lighting effects, including deep darkness and complete darkness... My Main Cammera's Clear Flags is set to: Solid Color, and Background is set to: black... so I was expecting that by disabling all lights, my Game window would look completely black, as there is no source of light at all... however I still colud see the objects on my scene... a little bit darker, but not enough to make the player to believe all lights are gone... then I remembered there is a Lighting window so I opened up and started playing with the parameters there... I set Ambient Source to: Color, Ambient Color to black and Ambient Intensity to: 0, some of the objects became dark gray but not completely black, while the rest was not affected at all.

All the Materials I'm using employ the Standard Shader with an Opaque Rendering Mode, the objects that were affected by the change in the ambient light have Metalic and Smoothness set to 0, and those not affected have Metalic and Smoothness set to: 1... ok... then I set Reflection Intensity to: 0... and this time I got what I was looking for, a solid black screen... However if I enable the lights again, the objects that have Metalic and Smoothness set to: 1, remain solid black.

This does not make any scence to me... if there isn't any light source and there's no ambient light either, then there's nothing to reflect, so regardless of the shader's parameters all objects should be rendered in solid black, regardless of the Reflection Source and Reflection Intensity parameters... I think the actual reflection intensity should be calculated as: AmbientIntensity*ReflectionIntensity in order to be coherent.

So the question is: How do you simulate deep darkness or complete darkness in a scene containing highly reflective objects???