GOOD ONES! GOOD ONES! GOOD ONES!
"1943" penny material" STEEL [I remember the gray coins, but I didn't know they were steel.]
"Corp. that once owned Hertz and Hilton" UAL [who knew?]
"100 cents" EURO [didn't know that either, but it makes sense]
"Little butter" KID
"Needing salt, perhaps" ICY [Do native Floridians know this?]
For "Rain, briefly" we have PRECIP. Okay, but precip. is not short for rain; it's long for rain. It is, however, short for precipitation.
The theme is in hiding because the word gall is not used to expose it for the solver. LETO could be changed to GALL, the others amended to fit, and ipso facto we have moved from the covert. :)