What is the main type of energy used to covert rocks into metamorphic rocks in the rock cycle?

Metamorphic rocks are usually formed by a combination of heat and pressure, as they form deep under the Earth's surface, so it is likely your answer is Heat.

Igneous rocks are formed by molten materials, and Sedimentary rocks are formed by formed by layers of sediment and debris.

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maybe because its impossible for balloons to lift a whole entire house.

evidence and logical support is essential for a scientist to do in order to maintain credibility. this is because no one can believe without any logic and without any evidence.hence a scientist can maintain credibility by proving himself and by answering logically so experiments prove very beneficial. logical hypothesis give conclusion which is acceptable. therefore, there are two main factors to maintain credibility by a scientist is evidence and logical support.