Elon Musk, Tesla CEO, stands in the foundry of the Tesla Gigafactory during a press event.Elon Musk, Tesla CEO, stands in the foundry of the Tesla Gigafactory during a press event.

After an SEC filing revealed that Musk acquired a 9.2% passive stake in the company, the stock is on track for its best day since its IPO.

After its public debut, the company closed up over 70%. The stock is down from its all-time high.

The outspoken executive is expected to take a more aggressive stance. He could increase his stake or take control of the company in order to push for change.

We would not be surprised to see him increase his stake even further, and possibly assume a more active role in the decision-making at the company, considering what a small investment this is for him.

Musk said he was considering building a new social media platform. The Securities and Exchange Commission is one of the regulators that the CEO dislikes.

Musk said on March 26 that failing to adhere to free speech principles undermines democracy.

The Securities and Exchange Commission subpoenaed Musk after he asked his followers if he should sell 10% of his stock.

In February, Musk accused the SEC of harassing him and trying to chill his free speech.

CNBC's Sam Shead contributed to the report.

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