生气 (shēng qì) is the most common everyday verb for 'to get angry' — it's a separable verb (生…气) so you can insert a subject, e.g. 生他的气 'be angry at him'. 发火 (fā huǒ) is more intense, meaning 'to lose one's temper', while 愤怒 (fèn nù) is a formal adjective describing deep, sustained anger.