Leo and Kate are the epitome of friendship goals.
The two of them had been fast friends since college.
3、birds of a feather
He'll like Tony-they're birds of a feather.
4、be(as)thick as thieves
I'm sure she tells Ruth everything we say-they're as thick as thieves.
5、joined at the hip
Those two are joined at the hip.They are always together.
It was a pleasure meeting you-I hope our paths cross again.
7、strike up a friendship
I struck up a friendship with John while we were on a business trip together.
A fair-weather friend isn't much help in an emergency.