Can anyone tell me what the purpose of a patch of red tacky stuff about 4" X 12" located in the bottom of the trunk is? Looks like a seal of some sort and there appears to be a metal plate underneath it.
At first I thought it was rust. It looks like it has melted some because of heat from the exhaust.
I'm in the process of installing new carpet and just not too sure what to think about this stuff since it is sticky and messy like red tar.
Any suggestions?

The red sticky stuff seals the plate in the hole. Leave it alone.

If it is melting, you have a leaky exhaust system.

Thanks for the comments. I now have a new exhaust system installed.