火

火车 was born in the steam age. The engine had a real fire heating water into steam. Modern electric trains have no fire, but Chinese kept the old name. That is why the story line 火车没有火 is a playful literal joke. “火车没有火。” (There is no fire on a train.) ── [《火车没有火》](/read/train-without-fire#s2)

When 火 is the thing, 很 describes it: 火很大. When 火 describes a person, shop, or song, 很 goes in front: 很火. So 这家店很火 means the shop is popular, not burning. 火很大 means the actual fire is large.

Entertainment headlines use 他火了 for sudden fame. In a fight, 老板火了 means the boss lost his temper. For plain anger, people often say 发火 or 火大. Context decides which fire you mean.

很火 describes fame or trendiness, not flames. For a real fire, say 着火了 or 厨房着火了. The verb 着火 means a fire has caught. Yelling 我很火 makes you sound trendy while the room burns.