Why won't Rigify deform my High Poly Mesh? probably sounds like a silly question that has already been answered 1000 times, but I've read through previous forums and none have been able to answer my question. 

I recently downloaded a free high poly 3d mesh of an astronaut from a royalty free 3d model site. The file was already saved as a .blend file and I'm intending to use it in a film I am currently working on, rigging isn't my strong point and I followed several simple tutorials using blender rigify and blendrig, however every time I go to connect the mesh to the bones using automatic weights, nothing happens when I go to pose mode, the model remains stiff and does not move. I've tried several different rig setups. 

I've joined the seperate meshes together and tried with and without the vertice groups, but no matter what I do the mesh won't deform in the slightest, I was wondering if this is a bug with rigify in Blender 2.79 or because the mesh is so high poly? ANy help is much appreciated. I've included a link to the original file as well as the file I have with a metarig set up. 

Thanks again, regards Nathan.

https://www.dropbox.com/s/ufss6yyqu4b2usf/ASTRONAUT.rar?dl=0

https://drive.google.com/open?id=15oooEuGrDG6xpSfs68FY8ibhwt9CxBxZ
It's hard to tell what's going wrong if you provide only your mesh without the rig you did.

But certainly, you can't do animation with a raw mesh of 2 billion triangles. It's just unmanageable. Performances will be below ground level, you wont be able to have correct control over the weights and deformations, ...

The common workflow is to work on a low poly mesh with an optimized topology for the needed animation's deformations and let the details be handled by the shader (via normal + height maps) and by some displacements with additional subdivisions when rendering.

As I just want to test your model for rigging, I used a decimate modifier in un-subdivide mode with an even iteration. The suit being a more complex organic part, I used Instant Meshes, it's certainly not the best solution but it a nice last hand option in my case.
Then I tried to use Rigify on it, and it went well. I had to do some weights assignments manually on some parts (especially the pockets and some parts of the helmet), but nothing fancy. So IMO you should work on obtaining animation ready models first.