Tesla Motors (NASDAQ:TSLA) reports third-quarter results today after market close. Thanks to a soaring stock price, Tesla will be held to a very high standard. Here are three metrics to watch.

First, however, let's unearth some background story.

In a very short period of time Tesla has garnered a massive following. It makes sense: Investors have been rewarded nearly five times over in just one year, Tesla's new Model S has received an impressive number of prestigious accolades, and the company is selling every vehicle it makes. And for anyone who has taken the time to take a test drive, it's common to walk away with a sense that you've just tasted the future.

Such enthusiasm surrounding the stock has turned the company's earnings report into something of a show. Cult-like fans on Tesla's forums actively discuss Tesla's business and even volunteer to share their VIN numbers to keep an estimate of the company's production rate.

Along with borderline euphoric enthusiasm among customers and the Street, however, comes a valuation that is very difficult to justify. Tesla's stock has hit levels that have seemingly priced in the most bullish assumptions. That said, key metrics will be under intense scrutiny when the company reports results.

Though it's difficult to say what items in the report may drive short-term price movements, I've identified three metrics that Foolish investors should keep tabs on to assess the company's long-term-growth trajectory.

Vehicle sales
As I've discussed in a previous articles, vehicle sales will be the most important metric to watch. If Tesla's short history of Model S sales is any indication of what could happen this quarter, Tesla will outperform its own guidance. Last quarter, Tesla beat guidance of 4,500 deliveries with 5,150 Model S sales. This quarter, Tesla has guided for "slightly over" 5,000 vehicle deliveries.

Given that Tesla is supply limited, if Tesla is able to substantially beat its own guidance, it will indicate that the company is making more meaningful progress on its production bottlenecks earlier than it expected. 

Gross profit margin
Even as Tesla's zero emission vehicle, or ZEV, credits continue to shrink as a percentage to total revenue, Tesla's gross profit margin continues to improve rapidly. When Tesla reported results last quarter, management maintained their ambitious goal to reach a non-GAAP automotive gross margin target of 25% (excluding ZEV credits) by Q4 this year. Hitting 13% last quarter, Tesla would need to report a non-GAAP automotive gross margin of about 19% this quarter to land halfway between last quarter's results and its fourth quarter goal.

Source: Data retrieved from quarterly filings and earnings calls from the first and second quarters of 2013. The gross profit margin reported in the chart refers exclusively to the company's automotive segment, using non-GAAP figures excluding zero-emission vehicle credits.

Guidance for 2014 and beyond
Last quarter was the first time the company gave us a number for 2014, expecting to hit annualized Model S sales of more than 40,000 vehicles by next year. In other words, Tesla is projecting to double its current annualized rate of deliveries of approximately 21,000 vehicles.

Given Tesla's premium valuation, investors should hope that Tesla has an improved outlook by either moving the time frame for 40,000 in annualized sales earlier or by showing confidence in a larger number.

Any guidance for 2014 and beyond would be helpful -- especially in light of the stock's very forward-looking price tag.

Though it will be important to keep an eye on these three metrics, investors shouldn't get too caught up in quarterly results. Given the stock's valuation, I'll likely remain on the sidelines. But that won't stop me from reevaluating my long-term thesis for the company if the storyline shifts.