The no-ding body panels were a plastic composite, not steel. The composite panels expanded and contracted in the cold and heat more than steal so Saturn frequently took a hit for fit and finish in reviews.
For 2007 they started using steel body panels on their new designs which allows them to get better marks for fit and finish.
Steel panels began their introduction in 2000 on the L-Series. The rear quarter panels on both the wagon and sedan were steel.
The Relay was the first official all-steel Saturn.
The hoods, roofs and trunks of Saturns have always been steel.