What is the purpose of the large plastic cover that stretches over my valve cover? Does it have a particular function? Are they just for looks? Or are they designed by the engineers to protect wiring? I believe its called an engine cover. (I bought a car that was missing this piece and I need to know if its critical)

I have a 2010 Toyota Corolla. What is the purpose of the large plastic cover that stretches over my valve cover? Does it have a particular function? Are they just for looks? Or are they designed by the engineers to protect wiring? I believe its called an engine cover. (I bought a car that was missing this piece and I need to know if its critical)

What is the purpose of the large plastic cover that stretches over my valve cover? Does it have a particular function? I believe its called an engine cover.

What is the purpose of the large plastic cover that stretches over my valve cover? Does it have a particular function? Are they just for looks? Or are they designed by the engineers to protect wiring? I believe its called an engine cover. (I bought a car that was missing this piece and I need to know if its critical)