What is the value of a 1937 aluminum US cent?

All genuine 1937 US cents were struck in bronze.

If your coin weighs the same as a standard cent it's not aluminum; an aluminum cent would weigh only about a gram.

If your coin is in fact substantially lighter than a genuine cent it could be either a fake or possibly a mint error struck on a blank intended for Another Country's coinage. To determine which, you'd need to take your coin to a knowledgeable coin dealer or examiner.