Heavy Metal & Hard Rock:

The 1970s 
Hard Rock: This genre includes bands like Led Zeppelin, Deep Purple, and Black Sabbath. These bands are considered to be the pioneers of heavy metal and their music is characterized by heavy guitar riffs, driving bass and drums, and powerful vocals.

Heavy Metal: This subgenre is characterized by its fast-paced, energetic sound and features bands like Judas Priest, Van Halen, and Kiss. These bands helped to define the look and sound of heavy metal and had a major impact on the genre.

Progressive Rock: This genre is characterized by its complex songwriting and incorporation of classical music influences. Bands like King Crimson, Emerson, Lake & Palmer, and Genesis are considered to be influential in this subgenre.
Classic Metal: This subgenre is characterized by its incorporation of elements of hard rock, blues, and progressive rock. Bands like Rainbow, Blue Öyster Cult, and Scorpions are considered influential in this subgenre.

New Wave of British Heavy Metal (NWOBHM): This movement emerged in the late 1970s and early 1980s and was characterized by its fast-paced, energetic sound. Bands like Iron Maiden, Saxon, and Diamond Head were influential in this subgenre and helped to bring a new level of technical proficiency and songwriting to the genre.

The 1980s
Was a significant decade for hard rock and heavy metal music. During this time, both genres experienced a great deal of commercial success and mainstream popularity. In the early 80s, hard rock bands such as Van Halen, Aerosmith, and Bon Jovi had a string of hit albums and singles, and their music videos received heavy rotation on MTV.

Glam Metal: A subgenre of hard rock, emerged in the mid-80s, characterized by its flamboyant fashion and make-up worn by its performers, and bands like Mötley Crüe, Ratt, and Poison were among the most popular in this subgenre.

Hair Metal/Hair Bands: In the late 80s, a subgenre of heavy metal emerged, bands like Guns N' Roses, Skid Row and Cinderella were among the most popular in this subgenre. Hair metal was characterized by its big hair, tight clothes, and often sexually suggestive lyrics.
Thrash Metal: This subgenre emerged in the early 1980s and is characterized by its fast tempos, heavy guitar riffs, and aggressive vocals. Bands like Metallica, Megadeth and Slayer are considered as some of the most popular and influential thrash metal bands of the 1980s.

The 1990s

The popularity of hair metal and glam metal began to decline, however many bands from the 1980s continued to have success in the 1990s, with bands like Metallica, Guns N' Roses, and Van Halen releasing successful albums and touring extensively.
Alternative Metal: Combines elements of heavy metal with other genres such as alternative rock, punk, industrial, and even funk. The result is a sound that is often harder and more aggressive than alternative rock, but less polished and commercial than mainstream heavy metal. Alternative metal bands often use unconventional song structures and time signatures, and incorporate elements of dissonance and experimentalism in their music. Notable bands in alternative metal include Faith No More, Helmet, Jane's Addiction, Tool, System of a Down, Slipknot, Disturbed, and Deftones which are considered to be among the most popular and influential bands in the genre and have contributed to the mainstream success of alternative metal.
Nu-Metal: A subgenre of alternative metal that emerged in the late 1990s. It is characterized by a fusion of heavy metal and other genres, such as rap, funk, and industrial music. Nu-metal is known for its use of heavy guitar riffs, downtuned guitars, and a mix of clean and screamed vocals. The genre also features a mix of other instruments like samples, electronic beats, and turntables. Bands like Limp Bizkit, Korn, Slipknot and Deftones are considered as some of the pioneers of the genre, and have contributed to the rising popularity of Nu-metal in the late 1990s and early 2000s.

Power Metal: A subgenre of heavy metal music that emphasizes a strong and powerful vocal delivery, often in the form of high-pitched singing. The music is typically characterized by fast-paced, highly technical guitar playing, and a strong emphasis on melody and harmony. Power metal is often associated with fantasy and science fiction themes, and many power metal bands use lyrics that tell epic stories or explore fantastical worlds. Some well-known power metal bands include Blind Guardian, Sabaton, Powerwolf and Helloween.
Female Fronted Heavy Metal: There is a wide range of styles within female-fronted heavy metal, and different bands may incorporate elements from various subgenres of metal such as traditional heavy metal, power metal, gothic metal, symphonic metal, and more. The vocal styles of female-fronted metal bands can vary as well, ranging from operatic and classically influenced vocals to powerful and aggressive singing. Bands like Nightwish, Within Temptation & Arch Enemy are popular.
Grunge: A subgenre of alternative rock that emerged in the Pacific Northwest region of the United States, particularly in Seattle, in the mid-1980s. The music is characterized by a heavy, distorted guitar sound, often using the "drop D" tuning, and a raw and unpolished vocal style. Lyrics often deal with themes of social alienation and apathy. Bands like Nirvana, Pearl Jam, Soundgarden and Alice in Chains are considered as the most popular and influential acts of the genre.
Post-Grunge: A reaction to the massive mainstream success of the grunge movement. Known for its focus on mainstream accessibility and more radio-friendly sound. Post-grunge bands often incorporate more melodic elements, and polished production values. Bands like Nickelback, Creed, 3 Doors Down, and Puddle of Mudd are considered as some of the most popular and influential post-grunge bands.

The 2000s

And beyond have seen a continuation of the trends and changes that began in the 1990s in the hard rock and heavy metal genres.

Nu-Metal & Alternative Metal: Bands that gained popularity in the late 1990s and early 2000s, such as Limp Bizkit and Slipknot, saw a decline in popularity, but new bands in the same vein, such as Linkin Park and Disturbed, took their place and continued to have commercial success.

Metalcore: A subgenre of heavy metal music that combines elements of heavy metal and hardcore punk. It originated in the 1980s and gained mainstream popularity in the 2000s. The genre features a mix of both metal and hardcore punk styles, including fast-paced, aggressive riffs and breakdowns, screamed and growled vocals, and lyrics that often deal with social and political issues. The genre also incorporates elements of melodic death metal, thrash metal, and other subgenres of heavy metal. Some of the most popular and influential metalcore bands include Killswitch Engage, As I Lay Dying, All That Remains, Trivium, and Avenged Sevenfold.