Carrying the deceased on a bier made of iron

We do not know of anything wrong with that. We know of
nothing wrong with carrying the deceased on something made of wood or on a
platform made of something other than wood, such as iron. But it is better
to use something light so that it will not be too difficult for those who
are carrying it, because when people carry it on their shoulders, it may
be difficult for them. 

But if the deceased is carried in a car (hearse), the matter
is broader in scope, although using something light is better in all cases.
Using a light board on which the deceased is placed and carried to the
graveyard is better than using something heavy. But as for it being wrong,
there is nothing wrong, in sha Allah, with it being made of iron or of wood.
But if this iron is light and does not cause any difficulty to the people
(who are carrying it), there is nothing wrong with that. But if it is heavy
it should not be used, so that it will not cause hardship for those who
carry it. End quote. 

Shaykh ‘Abd al-‘Azeez ibn Baaz (may Allah have mercy on him)