Short answers, pulled from the story.
The oldest surviving shields date to the Bronze Age. The very first prototype likely emerged during the Late Neolithic Age as a simple protection device against hand weapons like swords, axes, and maces.
Early iterations were not made of metal but rather from wood, animal hide, woven reeds, wicker, or even turtle shells. The Yetholm-type shields of the Bronze Age and the Iron Age Battersea shield are examples of metal shields that survive today.
The Ancient Greek hoplites used the aspis, a round, bowl-shaped wooden shield reinforced with bronze, as the cornerstone of the Greek phalanx formation. This shield was used by the Spartans to create a wall of protection that covered not only the individual but also their comrades to the left.
The term swashbuckler originated from the use of the buckler, which continued well into the 16th century. The buckler is a small round shield, typically between 8 and 16 inches in diameter, and was one of the few types of shields usually made of metal.
Zulu warriors carried large lightweight shields called Ishlangu made from a single ox hide supported by a wooden spine. This was used in combination with a short spear, known as an iklwa, and/or club.
The first type is the riot shield, which is used for riot control and can be made from metal or polymers such as polycarbonate Lexan or Makrolon or boPET Mylar. The second type is the bullet-resistant ballistic shield, also called tactical shield, which is typically manufactured from advanced synthetics such as Kevlar.