The possessive form is the mouse's barbecue.
Yes, no cats allowed.
You must find a simple metaphor to use.
You would say, 'the mouse's barbecue'.
you would have more fun at a dignified backyard barbecue
A very involved metaphor is often called an extended metaphor. This type of metaphor continues throughout a paragraph, stanza, or even an entire work, drawing out the comparison and exploring it in detail.
Metaphor
The Pinciotti family invited Eric over for barbecue, but he thought it would be awkward.
no..drama queen is not a metaphor
His voice thundered through the house.
No. One word does not make a metaphor. "Bob is groaning" would be the closest you could get, but that is a statement, not a metaphor.
A metaphor for Christmas would be: "Christmas was a beautiful as spring day!"