Here are the essential branches of the rock family tree:

• Blues rock — the root. Guitar-driven, 12-bar blues structure. Cream, Stevie Ray Vaughan
• Hard rock — louder, heavier riffs, but still melodic. AC/DC, Led Zeppelin
• Punk rock — fast, short, aggressive, anti-establishment. Ramones, Sex Pistols
• Metal — extreme distortion, complex arrangements, virtuosic playing. Black Sabbath invented it; Metallica popularized it
• Alternative/Indie — deliberately outside the mainstream, prioritizing artistic integrity. R.E.M., Pixies, Radiohead