Amplifying magnitude metric of received signals during iterative decoding of LDPC code and LDPC coded modulation. By appropriately selecting a metric coefficient value that is used to calculate the initial conditions when decoding LDPC coded signals, a significant reduction in BER may be achieved at certain SNRs. The appropriate selection of the metric coefficient value may be performed depending on the particular SNR at which a communication system is operating. By adjusting this metric coefficient value according to the given LDPC code, modulation, and noise variance, the overall performance of the decoding may be significantly improved. The convergence speed is slowed down so that the decoder will not go to the wrong codeword, and the moving range of the outputs of the decoder is restricted so that the output will not oscillate too much and will eventually move to the correct codeword.