I've never done this, so I can't say definitively that it won't work, but I wouldn't expect it to. It has to do with, among other things, how the metal conducts and holds heat. I doubt lead has the right properties. Also, precisely because it is softer than brass and has such a low melting point, I wouldn't try it. But feel free to do so and report …
I have been doing some hot foil stamping on book covers and spines (bookcloth) and I would appreciate any comments or information on using foundry type in a hot foil stamping machine. While foundry type is a softer metal than that used in hot foil type I think that it would work for small runs, maybe 2 or 3 covers. I base this on the fact that foundry type, which I understand is lead, has a melting point above 600 F degrees while hot stamping requires 300 degrees F or less.
I came across some good information from David S. Rose of Five Roses Press on the topic of Type for Hot Stamping and Foiling. His write-up provides a great overview of the 'types' of type. I thought it very well done. Well, I will be trying the foundry type and have some confidence that it will work. I will be cautious as I do not want to deal with the health issues of melting lead. I will post the outcome. I am hoping for a nicely stamped bookcloth cover and not a toxic paperweight.
http://www.fiveroses.org/stampingtype.htm