Metal braces are the standard brace used for all age groups. The brace is made of stainless steel, maybe self ligating (Damon or Innovation) or require some form of tie to hold in the orthodontic wire. Of all braces, metal ones are the strongest and less likely to break during treatment than other brace types.
Those braces you see the kids with, all colourful so it looks like fun, well they are metal braces with a little coloured ring which holds the wire in place. Of course, if you are not into colours, a plain ring can be used.