They kind of make me pucker also. Just like the steel grating on some bridges makes me pucker. Relax, no sudden changes and ride over it. The state highway departments never think of motorcycles when they do stuff like that.
Just another reason to have and read the book Proficient Motorcycling.
Steel plates belong to a category called edge traps and are in the Bobby Traps chapter of the book. In addition to picking a straight line path of travel to cross them, you must stay away from the edges where they lie. It you travel over/near an edge, that can 'trap' your wheels and cause the motorcycle to fall over.
Other examples of edge traps include RR tracks, curbs and uneven pavement.
From page 147, here are the riding techniques:
Weight on footpegs
Pick best surface, follow smooth lines
Steady throttle hand
Bike perpendicular to road surface
If crossing a spill or slippery surface, like ice, just add squeeze in clutch before the hazard, cross over, release clutch after hazard.
Its a shame - this used to be a part of the older MSF beginners class.