How are metamorphic rocks formed?

metamorphic rocks are formed from preexisting rocks as a result of further increase in temperature and pressure on a sedimentary rocks. the minerals making up  the rock start changing or metamorphosed into metamorphic rocks.

metamorphic rocks formed wheen pre-existing rocks affected by pressure and temperature that lead to forming metamorphic

metamorphic rocks formed wheen pre-existing rocks affected by pressure and temperature that lead to forming metamorphic and the grade of metamorphism is depending on the degree of the temperature and pressure 

Metamorphic are formed by temperature and pressure from sedimentary and igneous rocks.

formed from all types of rocks that exposed to a very high level of temperature and pressure .

metamorphic rocks are formed due to over burden pressure and empratue.

due to rises of temp and pressure the existing rocks in the earth transfer to form metamorphic rocks such as limestone is thermally decomposed to form marbles.  

Metamorphic rocks are created by the physical or chemical alteration by heat and pressure of an existing igneous or sedimentary material into a denser form. Due to the action of plate tectonics, compression, stress and shearing forces over long periods of time, rocks can be essentially warped and deformed, causing them to be compacted into a smaller volume of space.

Examples of metamorphic rocks are schist (converted basalt), quartzite (compressed sandstone), and marble (compressed limestone or dolomite).

Metamorphic rock are that change undergo original form due to heat temperature and pressure and chemical alteration  

Metamorphic rocks are formed from pre-existing rocks when these rocks are buried under intnse temperature and pressure regimes thus effecting a change in the chemical and physical properties of the previous rocks. In this way rocks such as gneiss is formed from granite.

Metamorphic rocks arise from the transformation of existing rock types, in a process called metamorphism, which means "change in form".The original rock (protolith) is subjected to heat (temperatures greater than to °C) and pressure ( bars),[2] causing profound physical and/or chemical change. The protolith may be a sedimentary rock, an igneous rock or another older metamorphic rock.