Wow!  You have really gotten into these unusual organisms!  Slime molds used to be thought to be a kind of primitive fungus, but modern genetic analysis of them puts them much closer to amoeboid protozoa.  In this case, they act like colonial amoeba that have unusual habits of reproduction through complex spore-forming structures.  The Wikipedia web site on slime molds is pretty good and if you look at the references, you can find some of the traditional publications as well as some more modern references.

In answer to your questions, slime molds are very adapted to survive environmental extremes of heat and cold, dry conditions and wet conditions.  They are generally most active during cool and wet seasons when they adopt the amoeboid state, moving around in mass, feeding on decaying organic matter.  When conditions become less than favorable, they may simply dry down in a mumified state, or sporulate so that the very resistant spores survive until the next favorable period.

Wow! -- Thanks, David. Very interesting! "Sporulate" is the best word I've learned all year! So you're saying that sporulatring is not about eating which is why they might choose metal or plastic to do it on? (May I include several to ask if they even are some kind of fungus or mold or what? First was on the siding on my house; two is on a falling-apart shed; & three is on an old tree limb that was cut off the tree. Thanks!)

I forgot to mention that when the slime molds decide it's time to sporulate, they often go considerable distances from where their food was located.  A common one in turfgrass apparently eats the thatch and other decaying matter, then creeps up the grass stems, to the blades where they cover them with tiny round gray balls (spore masses).  My favorite species is Stemonitus which forms spore masses that look like neat rows of tiny trees.  My least favorite is the one that is commonly called "dog barf fungus!"  This usually forms a orange to brown spore mass on the surface of mulch that has been kept too wet.  It really looks like its common name!

Wow -- that is so interesting! Why would they travel far from food to, essentially, reproduce? Is this a case of "only the strong survive"? Thank you! I love the stemonitus (I guess it's that final U that keeps it from being a disease). I saw one here -- I'll include. Meanwhile, any uesses in those couple I included in the second email, and I know this may not be fusca, and now I realise I spelled Stemonitus wrong....

It looks like you may have five or six orders of the slime molds figured!  I would look at this web site to help in identifications.  In many cases, you will only be able to go to order or family level as there appear to be many species, even in each genus!

http://slimemold.uark.edu/index.htm

BTW, no need to respond as this crazy system requires me to respond to any of your responses!  Otherwise, it keeps reminding me that I haven't answered a question!  LOL!