Pro tip from my street: car hoods make terrible porch ramps
Honestly, my neighbor tried using a bent sedan hood as a ramp for his lawnmower and it slid right off into his rose bushes. Tbh, I'm still laughing but now I'm scared to ask what he'll try next.
Forget the slick paint, what about the hinge points? Those things aren't built to take weight from the side, so they could snap and whip back. I mean, that's a whole new level of danger right there.
I read a DIY forum where someone used a fridge door as a ramp. It bent in the middle under a wheelbarrow. Car metal is too slick and weak for weight. Your neighbor's rose bushes are lucky it was just a lawnmower. Saw a video of a guy trying a car trunk lid. Same slide-off disaster.
Actually, car hood metal isn't always that weak. The problem is it's a single unsupported sheet. A fridge door has some internal bracing, but it's still hollow. A proper ramp has a folded or ribbed structure across its whole length, so the force gets spread out. That's why even thin steel can work if it's shaped right.
My cousin tried an old car hood for his ATV ramp last summer. The glossy paint caused tire spin before any bending. @thea602 has a point on weak metal, but surface finish matters too. Without grip, even thick steel just slides out.