Are metal steel strings OK for classic violin? Never played violin, you know.
This is very broad.
Classical strings, as noted in user25984's answer, are actually made of a long core (synthetic, metallic or rarely gut) and of a wound, generally of steel, sometimes of silver.
Baroque strings are gut.
Are metal steel strings OK for classic violin?
Yes, they definitely are ok for classical violin. There is a large range of colors you can achieve by choosing this or that string set. Thomastik strings are very known strings, cheap yet producing good sound.
I personally like Vision Titanium Orchestral string sets, for their bright sound, their responsiveness and their long life time.
It should be noted, however, that the kind of influence string has on sound can take some time to be aware of.