Why does nuclear fusion, which releases energy for lighter elements, cease to be an energy source when iron is formed?

Answer

Iron-56 possesses the highest binding energy per nucleon

Iron-56 has the highest binding energy per nucleon of all elements; fusing elements lighter than iron releases energy, but fusing iron nuclei consumes energy rather than producing it.

Why does nuclear fusion, which releases energy for lighter elements, cease to be an energy source when iron is formed?
ElementastronomyProductionstar