The primary cause of lead's toxicity is its interference with a variety of enzymes because it binds to sulfhydryl groups found on many enzymes.[22] Part of lead's toxicity results from its ability to mimic other metals that take part in biological processes ... Among the essential metals that lead displaces in this way are calcium, iron, and zinc.[186]

The brain is the organ most sensitive to lead exposure.[77] Lead can pass through the endothelial cells at the blood brain barrier because it can substitute for calcium ions and be taken up by calcium-ATPase pumps.[203]

The targeting of NMDA receptors is thought to be one of the main causes for lead's toxicity to neurons.[202]

The half-life of lead in bone has been estimated as years to decades, and bone can introduce lead into the bloodstream long after the initial exposure is gone.[182][183][184] The half-life of lead in the blood in men is about 40 days, but it may be longer in children and pregnant women, whose bones are undergoing remodeling, which allows the lead to be continuously re-introduced into the bloodstream.[26]

https://en.wikipedia.org/wiki/Lead_poisoning

Stainless steel is generally considered to be biologically inert. However, during cooking, small amounts of nickel and chromium leach out of new stainless steel cookware into highly acidic food.[115] Nickel can contribute to cancer risks—particularly lung cancer and nasal cancer.[116][117] However, no connection between stainless steel cookware and cancer has been established.

https://en.wikipedia.org/wiki/Stainless_steel

Lead is very different in its toxicity. Chromium is not nearly as toxic, and in fact trivalent chromium is an essebtial nutrient:

Trivalent chromium is a trace mineral that is essential to human nutrition

https://en.wikipedia.org/wiki/Chromium_toxicity

Of course wikipedia isn't an official source, but almost all statement's link to reliable sources