Hi! I have written an article on UkuGuides about the types of strings and which are most frequently used on ukuleles. You can find it here: https://ukuguides.com/information/buying-the-right-ukulele-strings/
Do you truly mean steel strings or wound metal strings? You need a very specifically constructed ukulele if you want to used steel strings. Wound metal strings are used sometimes on ukuleles, but for the “true” ukulele sound I’d go with nylon (Aquila) strings.