Tech giant Apple (NASDAQ:AAPL) is scheduled to report its financial results for its fiscal second quarter after market close on Tuesday, May 1. Given Apple's accelerating year-over-year revenue growth rates recently, investors will be looking to see if the iPhone maker has been able to keep up this momentum. In addition to checking on total revenue, investors may want take a look at other key metrics like gross profit margin, growth in services and other products revenue, and more.

Here's a preview of what to expect from five key metrics.

An iPhone X being splashed by water.

iPhone X. Image source: Apple.

1. Revenue growth

Ever since returning to growth in its first quarter of fiscal 2018, Apple's growth has been picking up steam. In Apple's most recent quarter, the company posted record revenue of $88.3 billion -- up 13% from revenue of $78.4 billion in the year-ago quarter. This year-over-year growth was up from 7% and 12% year-over-year revenue growth in Apple's third and fourth quarters of fiscal 2017, respectively.

For Apple's second quarter, management guided for revenue to be between $60 billion and $62 billion. The midpoint of this guidance range implies 15% year-over-year revenue growth, suggesting Apple's growth could accelerate yet again.

2. Gross margin

Guiding for a gross profit margin of 38% to 38.5% in its second quarter, compared to a gross profit margin of 38.9% in the year-ago quarter, Apple anticipates a slight year-over-year decline in profitability. The expected pressure on its gross margin likely reflects higher costs associated with Apple's latest iPhone models, particularly its iPhone X, which sports a redesigned form factor. In addition, management said in its second-quarter earnings call that higher memory prices are expected to be a headwind for costs during the period.

3. Services

Apple's services business has been an increasingly important catalyst for the tech company. Indeed, the segment is now Apple's second largest. iPhone accounts for 62% of Apple's trailing-12-month revenue, while its services segment represents 13% of revenue. Apple's Mac segment comes in third at 11% of revenue.

Apple's services revenue is growing rapidly, rising 18% year over year in Q2, or up 27% when adjusting to exclude the impact of an extra week in the year-ago quarter.

Investors should look for similarly strong growth from the segment in Q2.

4. Other products

Though Apple's other products segment is much smaller than services, accounting for just 6% of trailing-12-month revenue, it's growing even faster than services. In Apple's most recent quarter, other products revenue increased 36% year over year, or 47% when excluding the impact of an extra week in the year-ago quarter.

Apple's other products segment was helped by notable strength in wearables, or revenue from Apple Watch, AirPods, and Beats products. Total revenue from wearables during the period was up 70% year over year in Q2, Apple said in its first-quarter earnings call.

Investors should look for this momentum to continue in Q2.

5. Revenue guidance

Finally, investors will want to look to see what sort of revenue guidance Apple provides for its third quarter. This will give investors insight into how well its latest iPhone cycle is performing. Since the iPhone accounts for well over half of Apple's revenue, management's outlook for total revenue can give investors an idea of the trajectory Apple is expecting for iPhone sales.

For Apple to keep up its year-over-year revenue growth, it will need to guide for third-quarter revenue above the $45.4 billion in revenue the company reported in its fiscal third quarter of 2017. Guidance below this level could suggest Apple's latest iPhones aren't performing well.