Black coat under car
I know nothing about car maintenance and I've been messing under my car to install a trailer hitch. Worked great but I found this thick black sticky coat sprayed under part of the chassis. It's not everywhere, just some choice areas. I'm just curious what it is. I had to cut a piece of metal to fit the trailer hitch and that exposed some bare metal and I was thinking of just re-coating this to prevent rusting. What is that black substance?