Explanation:

- Iron is the backbone of the Indian metallurgical industry, crucial for infrastructure and development. It is not the second but the most important metallurgical industry in India.

- Copper plays a vital role in electricity and communication sectors, but it is less significant in comparison to aluminium and iron.

- Aluminium is indeed very significant due to its extensive use in various industries such as aerospace, automotive, and packaging. It holds the position of the second most important after iron.

- Zinc is used to protect steel from corrosion, primarily via galvanization, but it trails behind aluminium in terms of its overall industrial importance.