What happened

After a big day yesterday in which its stock rose 27%, Twitter (TWTR) is once again moving higher today. Shares had risen as much as 9.5% in pre-market trading but gave back much of those gains and were up about 3.3% as of 10:38 a.m. ET on Tuesday.

So what

Shares went flying yesterday after filings from the Securities and Exchange Commission (SEC) showed that Tesla founder Elon Musk had taken a 9.2% passive stake in the company. Today, SEC filings showed that Musk will join Twitter's board of directors, signaling that he could play a role in shaping the future of the social media giant.

Green squiggly line moving upward.

Image source: Getty Images.

"Through conversations with Elon in recent weeks, it became clear to us that he would bring great value to our Board," CEO Parag Agrawal tweeted today. Former Twitter CEO Jack Dorsey also tweeted that Musk "cares deeply about our world and Twitter's role in it."

The news this week certainly seemed to catch the market off guard, considering that just a few weeks ago, Musk publicly criticized Twitter in a tweet, asking a question to his audience: "Free speech is essential to a functioning democracy. Do you believe Twitter rigorously adheres to this principle?" Musk also said earlier this year that he's considered building his own social media platform.

Now what 

While Musk could still build his own social media platform, and you never know how his time on Twitter's board will go, these moves make it more likely that he and his 80.5 million followers are likely here to stay on Twitter.

Having someone like Musk, one of Twitter's most influential profiles, on the board might also make finding and rolling out solutions to some of the free-speech issues Twitter faces a bit easier as well. It won't solve everything, but it's certainly good news for the company.