It's a classless system, so characters can wear whatever they have the stats to equip. Metal/str, leather/dex, and cloth/int requirements mean that a character is likely to wear armor that is thematically associated with a given style, but if your archery-focused character has enough str or int then they can use metal or cloth armor without a problem.
Metal armor will have better defense than an equivalent leather piece, and both will have better defense than an equivalent cloth piece. Beyond that, leather and cloth have default movement and (usually) initiative bonuses, while metal armor has a default penalty (which can be removed by fitting it at an anvil). Leather armor typically has a small amount of poison resistance built in, while metal armor typically has a moderate amount of elemental resistance built in.
Magical enhancements on any of them vary widely.
