Final answer:
Metamorphic rocks are characterized by factors including heat, which allows mineral restructuring; pressure, which can create foliation; and the chemical composition of the parent rock, which influences the new mineral assemblage and texture.
Step-by-step explanation:
The characteristics of metamorphic rocks are influenced by three main factors: heat, pressure, and the chemical composition of the parent rock. Heat is essential as it 'softens' the rocks, allowing mineral restructuring. Pressure, either from the weight of overlying material or tectonic forces, can cause minerals to re-orientate, leading to the formation of foliation. Lastly, the chemical composition of the protolith, or parent rock, significantly contributes to the resulting metamorphic rock's new mineral assemblage and texture. Some metamorphic rocks exhibit foliation, a textural feature characterized by the parallel alignment of platy minerals, due to directed pressure. In contrast, other rocks might be non-foliated when minerals exhibit no preferred orientation or when the rock's mineral composition is not conducive to foliation.