Symphonic metal is a subgenre of heavy metal music which combines the heavy drums and guitars of metal with different elements of orchestral classical music, such as symphonic instruments, choirs and sometimes a full orchestra.
https://en.wikipedia.org/wiki/Symphonic_metal

Death metal is an extreme subgenre of heavy metal music. It typically employs heavily distorted and low-tuned guitars, played with techniques such as palm muting and tremolo picking, deep growling vocals, aggressive, powerful drumming featuring double kick or blast beat techniques, minor keys or atonality, abrupt tempo, key, and time signature changes and chromatic chord progressions. The lyrical themes of death metal may invoke slasher film-stylized violence,[3] religion (sometimes Satanism), occultism, Lovecraftian horror, nature, mysticism, mythology, philosophy, science fiction, and politics,[4][5] and they may describe extreme acts, including mutilation, dissection, torture, rape, cannibalism, and necrophilia.

https://en.wikipedia.org/wiki/Death_metal