Do they come with screws? And are they stainless steel?

The screws and plastic spacers are included, but the screws are not very strong if you are using pressure treated joists. Someone on another site recommended pre-drilling every fastener. The starter clips are not included.

Description says plastic fasteners. But the picture is the metal ones.

Thank you for your question. Fasteners clip between each board for a seamless, fastener-free look. No screws, no screw holes, nothing to interrupt the smooth texture and comfortable feel of your new Trex® deck. Includes plastic fastener with pre-set screw