Cast iron has thermal mass. It will cool down the least when food is added. It also will not buckle like, say, a thinner carbon steel pan. This is important

Cast iron has thermal mass. It will cool down the least when food is added. It also will not buckle like, say, a thinner carbon steel pan. This is important if you want to get the pan hot and for it to stay hot. Common for searing large cuts of meat.