MADE - a VERB or an ADJECTIVE in the example: "This car is MADE of steel." Please, help

I understand that the word MADE is a verb by default, and this is an example with it in a passive voice:

"The cars are made of steel."

But can it be an adjective? As a characteristic of something, like in this example:

"This car is made of steel" or "This desk is made of hard wood"

Thanks

Cannot find the reference, forgive me, but here goes.

The verb in these cases is the word 'is', not 'made'. 'Made of' works as an adjective to describe the nature of the car and the desk. It is [very] old fashioned but still correct to say that the desk is 'of wood' and that the car is 'of steel'. The idiom Made of describes the fundamental nature of the object, not its process of construction or action of being made.