sticky pads

Hello all I was reapplying thermal paste to my msi 970 (4gb twin frozr) and I noticed something stuck behind one side of the radiator. I'm not entirely sure what the substance is but is there any reason this is stuck behind the radiator and if necessary, can I remove it? It's that long...

I bought the Commander Pro and it came with 2 sticky pads but in the manual, it said not to attach them to components that could be weak to magnets. I'm left wondering if the pads themselves will influence or the Commander Pro. I put it (the commander only, without the pads) on the other side of...