steel
Iron is the main ingredient, but it usually contains carbon too.
Iron
because its a strong metal
Any metal that isn't too soft can be used. Stainless steel, regular steels, brass. Even aluminium. Titanium can be used as well.
Metal plastic and all sorts of manufacture
Manhole covers are used for many things. Manhole covers are used to cover up holes in the ground where sewage can be found in order to protect people.
Those metal things in the middle of the road are called "manhole covers" or "manhole lids." They are used to cover openings to underground utility lines and provide access for maintenance and repair work.
Round manhole covers are generally used over square manholes because they cannot fall through the manhole openings. There is a chance that if square manhole covers are used they can be turned at an angle and fall through the manhole opening. Round manhole covers can be moved more easily as well.
Iron is the main ingredient, but it usually contains carbon too.
If they were made of wood they would rot and have to be replaced frequently. The metals used are also inexpensive.
steel
Magnesium
a man dog is a good type of metal
Magnesium
Magnesium.
A circular manhole cover is used because it cannot fall into the hole it covers regardless of its rotation. This design simplifies installation and removal of the cover, reduces the risk of accidents, and is more cost-effective to manufacture.
Man-hole covers (inspection covers) are made from heavy, thick cast-iron. Gates can be made from wood or metal.