Here's the 'most important metric' as Wall Street gears up for Apple's upcoming earnings report

• Apple is scheduled to report its fiscal fourth-quarter earnings on Thursday after the market close.
• Investors are focused on Apple's iPhone sales in China and the company's outlook for the holiday quarter.
• Here's what Wall Street expects from Apple's upcoming earnings report.

All eyes are on Apple as it is scheduled to report its fiscal fourth-quarter earnings on Thursday after the market close.