Very nice question!

Let's look at the frequency distribution of a halogen lamp:

[![enter image description here][1]][1]

You can see that all frequencies are present (hence the white color). The temperature of the burning lamp is about $800$ Kelvin. If you polarize the beam nothing, in particular, should happen for the photons have a random distribution of polarization. The intensity should obviously get less.  
Did you change the settings of the camera? I think you have to (why did you use two filters, by the way?).

I can think of nothing else to conclude that the metal reflects the light in such a way to produce your observation(s). Paper reflects in a completely different manner. Try using another metal.


Maybe this is of some importance (though it's not related to reflection)
One can read the following question [here][2]:

>How can I obtain a circularly polarized light with Tungsten Halogen light?
I'm the graduate student Po-Yang Wu of Taiwan National Cheng Kung University.
I have bought an optical element (AQWP05M-1600) form Thorlab company, but I have some problems now.
The problem I want to ask is that whether I can use the combination of a polarizer (Glan-Thompson, 300~2300nm) and achromatic quarter waveplate (1100~2000nm) to generate a circularly polarized light with Tungsten Halogen light (350~2300nm).
Or the light source only can be a laser light source?


  [1]: https://i.sstatic.net/uDBSz.png
  [2]: https://www.researchgate.net/post/How_can_I_obtain_a_circular_polarized_light_with_Tungsten_Halogen_light