Metalcore is a fusion genre combining elements of extreme metal and hardcore punk. The word is a portmanteau of the two genres. Among other styles blending metal and hardcore, such as crust punk and grindcore, metalcore is noted for its use of breakdowns, which are slow, intense passages conducive to moshing.  Pioneering metalcore bands—such as Integrity, Earth Crisis and Converge,   all of which had formed by 1990—are described as leaning more toward hardcore, with their style sometimes being called metallic hardcore , whereas later bands—such as Killswitch Engage, All That Remains, Trivium, As I Lay Dying, Bullet for My Valentine, and Parkway Drive —are described as leaning more towards metal.  Pantera  and Sepultura  (who influenced Trivium, Atreyu, Bleeding Through and Unearth) have been particularly influential to the development of metalcore in the 2000s, which saw many bands in the genre achieve commercial success.
Black Flag and Bad Brains, among the originators of hardcore, admired and emulated Black Sabbath. British punk rock groups such as Discharge and the Exploited also took inspiration from heavy metal. The Misfits put out the Earth A.D. album, becoming a crucial influence on thrash. Nonetheless, punk and metal cultures and music remained fairly separate through the first half of the 1980s. Cross-pollination between metal and hardcore eventually birthed the crossover thrash scene, which gestated at a Berkeley club called Ruthie's, in 1984. The term "metalcore" was originally used to refer to these crossover groups.  Hardcore punk groups Corrosion of Conformity, D.R.I. and Suicidal Tendencies played alongside thrash metal groups like Metallica and Slayer. This scene influenced the skinhead wing of New York hardcore, which also began in 1984, and included groups such as Cro-Mags, Murphy's Law, Agnostic Front and Warzone. The Cro-Mags were among the most influential of these bands, drawing equally from Bad Brains, Motörhead and Black Sabbath. Cro-Mags also embraced straight edge and Krishna consciousness. Another New York metal-influenced straight edge group of this time period is the Crumbsuckers. 1985 saw the development of the hardcore breakdown, an amalgamation of Bad Brains' reggae and metal backgrounds, which encouraged moshing. Agnostic Front's 1986 album Cause for Alarm , a collaboration with Peter Steele, was a watershed in the intertwining of hardcore and metal.
Origins (1980s and 1990s)
Between 1984 and 1995, a wave of metallic hardcore bands emerged,  including Hogan's Heroes, Integrity, Earth Crisis, Converge, Shai Hulud,    Judge, Strife, Rorschach, Vision of Disorder Hatebreed, and Disembodied.
Integrity drew influence from the hardcore band G.I.S.M. and the thrash metal band Slayer, with others like Septic Death, Samhain, Motörhead and Joy Division. Earth Crisis, Converge and Hatebreed  borrowed from hardcore punk and death metal. Earth Crisis's albums Firestorm , Destroy the Machines and Gomorrah's Season Ends were particularly influential to the (further) development of the genre.   Biohazard, Coalesce and Overcast were also important early metalcore groups. Journalist Lars Gotrich wrote, "Along with key records by The Dillinger Escape Plan and Botch, Give Them Rope (1997) is an underground milestone that helped (further)........ what was soon (universally) called 'metalcore'. At the risk of sounding too reductive—metalcore was the natural progression where extreme metal and hardcore met, but with spiraling time signatures that somehow felt more aggressive."  Shai Hulud's 1997 album Hearts Once Nourished with Hope and Compassion became especially influential in the latter part of the decade.   
In the early 2000s, metalcore started to gain more prominence, with several independent metal labels, including Century Media and Metal Blade, signing metalcore bands. A new subgenre, melodic metalcore, strongly influenced by Swedish melodic death metal, has formed and quickly came to the forefront of metalcore's rise to popularity. By 2004, Killswitch Engage's The End of Heartache ,  Shadows Fall's The War Within ,  and Atreyu's The Curse debuted at numbers 21, 20, and 36, respectively, on the Billboard album chart. Also, in 2006, Atreyu's third studio album, A Death-Grip on Yesterday debuted at Number 9 on the Billboard 200, only to be followed up by 2007's Lead Sails Paper Anchor , which debuted at Number 8. All That Remains' single " Two Weeks " peaked at number 9 at the Mainstream Rock Tracks chart in the U.S. The song peaked on the Modern Rock Tracks chart at number 38. In 2007, the songs " Nothing Left " by As I Lay Dying and " Redemption " by Shadows Fall were nominated for a Grammy award in the "Best Metal Performance" category. An Ocean Between Us (the album that included "Nothing Left") itself was a commercial success, debuting at number 8 on the " Billboard 200 ".
In 2008 Welsh metalcore band Bullet for My Valentine's second album, Scream Aim Fire , went straight to number 4 on the Billboard 200,  which was later surpassed in 2010 by their third album Fever , which debuted at number 3 selling more than 71,000 copies in its first week in the United States and more than 21,000 in the United Kingdom. Bullet for My Valentine's 2006 album The Poison was certified gold by the Recording Industry Association of America (RIAA).  Underoath's fifth album Define the Great Line , released in 2006, peaked at number 2 on the Billboard 200 charts, selling 98,000 copies in its first week. 
Trivium have met with success, making the top 25 positions on charts in several countries, including the United States, and top 10 positions in both Australia and the United Kingdom (where it even achieved Gold status). Hatebreed, God Forbid, and As I Lay Dying have also charted.   The Devil Wears Prada achieved some commercial success with their album, With Roots Above and Branches Below , peaking at number 11 on the Billboard 200 upon its release.  Underoath's album Lost in the Sound of Separation reached number 8 on the Billboard 200 and sold 56,000 copies in its first week of sales in the United States alone,  with Killswitch Engage's self-titled fifth album reaching number 7 on the same chart and selling 58,000 copies. 
By the early 2010s, metalcore was evolving to more frequently incorporate synthesizers and elements from genres beyond rock and metal. The Devil Wears Prada's 2011 album Dead Throne (which sold 32,400 in its first week)  reached number 10,  on the Billboard 200 chart. In 2013, British band Bring Me the Horizon released their fourth studio album Sempiternal to critical acclaim. The album debuted at number 3 on the UK Album Chart and at number 1 in Australia. The album sold 27,522 copies in the US, and charted at number 11 on the US Billboard Chart, making it their highest charting release in America until their follow-up album That's the Spirit , on which they abandoned metalcore, debuted at no. 2 in 2015.
In recent years there has been an underground revival of the early metallic hardcore style, with bands like Kublai Khan, Code Orange, Beartooth, Baptists and Knocked Loose breaking out of the underground to achieve varying levels of success.       Counterparts show a similar style but with more melancholic tones, leading to them being categorized as melodic hardcore. 
Metalcore is known for its use of breakdowns, in which it was preceded by heavy hardcore. Metalcore singers typically perform screaming,  a vocal technique developed in the 1980s and characteristic of 1990s metalcore. More recent bands often combine this with the use of standard singing, usually during the bridge or chorus of a song.  The death growl technique is also popular.
The instrumentation of metalcore includes heavy guitar riffs, double bass drumming, and breakdowns.  Drop guitar tunings are often used. Most bands use tuning ranging between Drop D and A, although lower tunings, as well as 7 and 8 string guitars are not uncommon. Drummers typically use a lot of double bass technique and general drumming styles across the board. Blast beats are also heard at times. According to author James Giordano, "tempos in metalcore tend to be slower than those found in thrash metal".
Metalcore emerged from the subcultures of heavy metal and hardcore punk. Some metalcore groups, such as Converge have lyrically focused on personal anguish and experiences of failed romantic love.  Meanwhile, there has been a significant number of Christian metalcore bands, building on the genres of Christian metal and Christian hardcore ; bands with Christian members include Zao,  Demon Hunter, Haste the Day, For Today, As I Lay Dying, The Devil Wears Prada, Norma Jean, August Burns Red, Texas in July, Oh, Sleeper and Underoath.  
Emerging from the hardcore genre, some bands are influenced by environmentalism, animal rights, anti-corruption and anti-capitalism.
The early 2000s included a wave of metalcore bands who placed significantly greater emphasis on melody. Melodic metalcore bands include Avenged Sevenfold, As I Lay Dying, Trivium, Dead by April,  All That Remains,  Atreyu,  Bullet for My Valentine,  Bury Tomorrow,  Darkest Hour,  Shadows Fall, and August Burns Red.    These groups took major influence, cues, and writing styles from Swedish melodic death metal bands, particularly At the Gates,  Arch Enemy, In Flames and Soilwork.  Melodic metalcore often employs clean vocals.  
Mathcore began with the mid-1990s work of Converge,  Botch   Eso-Charis  and The Dillinger Escape Plan.  The term mathcore is meant to suggest an analogy with math rock. Mathcore is characterized by increased speed, technical riffing, and unusual time signatures.   Bands such as Fear Before also combine the metalcore sound with odd time signatures, as well as progressive elements. 
Deathcore is a fusion of metalcore and death metal.    Deathcore is defined by breakdowns, blast beats and death metal riffs.   Bands may also incorporate guitar solos and even riffs that are influenced by metalcore.  New York-based death metal group Suffocation is credited as one of the main influences for the emergence of deathcore. Some examples of deathcore bands are Suicide Silence,  Whitechapel,  Knights of the Abyss,  Carnifex  Chelsea Grin,  Impending Doom,  and Emmure. 
Electronicore describes a stylistic fusion of electronic music and metalcore.  Notable artists of this genre have originated from the United Kingdom, the United States,   Australia,  Canada,  France,  Hong Kong  and Japan. 
Progressive metalcore is a fusion of progressive metal and metalcore characterized by highly technical lead guitar and djent -influenced breakdowns.    Practitioners of the genre often rely heavily on "atmospheric" elements and complex instrumentation.  
Nu metalcore is the musical fusion of nu metal and metalcore originating in the 2010s.  Many notable groups take influence from deathcore, R&B,  post-hardcore  and industrial metal.  Metalcore and deathcore groups such as Emmure,    Of Mice & Men,    Suicide Silence,   and Issues   all gained moderate popularity drawing influence from nu metal and metalcore.