Straight fire is a common Aussie slang. It's used to describe something/someone so unperceivably hot, that just saying hot doesn't do justice. In order for someone/something to be straight fire, the majority of your squad must agree with it. Fire emoji is a good synonym of straight fire.
Random hot girl - Hey Vin
Vin - Damn girl, looking straight fire 🔥🔥
Random hot girl - what
Vin - what
The whole squad - Oi boys, check this girl out.. fuck I swear she is straight fire, holyyyyy
Jordo - Nah mate, I have seen better