alt Hacker NewsLineotype they use lead letters. They use an alloy. There was a lot of lead, but there's also other metals in it because lead is too soft to be useful in a press. The alloy had the interest stream property that it has very low shrinkage when it cooled.
Classic letterpress type is lead, antimony and tin, but I don’t know if the so-called hot lead machines used that particular alloy. People usually just call it all “lead type” though.