The only common or rare dragon of category 5 I have is space being which doesn't have a metal element.
I have few cat 4 dragons with metal element but all of them are max level 10. From my high level dragons (20 and above) only the war dragon is cat 4.
It is interesting that next season will be only 2 weeks instead of 3 like all other until now.
All in all these random requirements for each season are very annoying. They would be less annoying if the dragons were limited to level 15 or 20 or something else requireing less food to reach full potential. Even for seasoned players it is worthless to invest into dragons which they will probably never use again.