Metal core

Metalcore is a subgene of heavy metal, The term took on its current meaning in the mid-1990s, describing bands such as Earth Crisis, Deadguy and Integrity

                                                                      Earth Crisis
What makes metalcore different from other subgenes is the powerful breakdown before the chorus. The slow tempo and strong rythm of those breakdown will cool down the audiences before other exciting riffs.
Some of the modern famous metalcore bands is Killswitch engage, As I lay dying, Parkway drive

                                            (Adam Dutkiwicz-guitarist of killswtich engage)

                                                                (As I lay dying)
Metalcore is the target of many modern rock bands these day because of the beautiful rythm it carries, often in the middle of the song, and set it apart from its mother-heavy metal which totally includes heavy riffs and screaming voice.
These day, there are even lots of different subgene of metalcore like: popcore, crabcore, technical metalcore,...and this branch of metal would develop more in the future of rock industry