Two things are upon us: school and fall. Both are rich fodder for metaphors. Every calendar you see will either have trees turning read, or back to school motifs.
Find a calendar and look at the picture for September. Use a metaphor to describe the picture. (This can be a helpful exercise later when you're picturing a scene in your head for a story.)
Oh, and try to not use the word 'like'. I've resisted for sometime now because it was so comfortable and easy to define metaphors as 'A is like B'. But that's technically a simile. For it to be a metaphor, if you're a purest, it's a little more 'A is B'.
Example: (Highlight the text if you need inspiration.)
Metaphor: As the hungry beast of color ravaged the forest, making it bleed with reds and oranges, the sad trees who were old were devoured early, the best of oncoming winter leaving their white bones to shimmer in the fall sunset.
Simile: Fall was like a hungry beast, ravaging the forest and leaving blood red leaves in its wake.