To forward function parameters to a cmdlet, use $psboundparameters automatic variable and splatting. Here is a sample:
function Get-BIOS($ComputerName, $Credential) { Get-WmiObject Win32_BIOS @psboundparameters }
Your function Get-BIOS works both locally and remotely. Only the parameters submitted by the user will actually be forwarded to Get-WmiObject.