Why weren't METAL SHIELDS more POPULAR in history?

Most shields in history have been made from organic materials, usually wood or leather. But METAL was used for SHIELDS also - so why weren't metal shields more popular in history? ▼3 extra EXCLUSIVE videos each month on PATREON, which make this channel possible:   / scholagladiatoria   ▼Facebook & Twitter updates, info, memes and fun:   / historicalfencing     / scholagladiato1   ▼Schola Gladiatoria HEMA - sword fighting classes in the UK: https://www.swordfightinglondon.com ▼Matt Easton's website & Pinterest: https://www.matt-easton.co.uk/ https://www.pinterest.co.uk/matt_east... ▼Easton Antique Arms - antique swords for sale: https://www.antique-swords.co.uk #archaeology #shield #history