In Monday's stock market activity, Cigna and Macy's emerged as the biggest gainers, while BlackBerry and several crypto stocks faced declines. Here's a closer look at the notable movements in the market:

Cigna (CI) saw its shares surge over 9% after announcing that it has abandoned its plans to merge with Humana (HUM). The decision was made due to an inability to reach a consensus on financial terms, including pricing. Instead, Cigna intends to pursue bolt-on acquisitions and has authorized an additional $10 billion in stock buybacks. This move brings the total amount of its repurchase authority up to $11.3 billion. Following the announcement, Humana's shares also rose by 2%.

Meanwhile, Macy's (M) experienced a significant jump of 20% following a $5.8 billion buyout offer from Arkhouse Management and Brigade Capital Management. The proposed buyout values the well-established department store chain at $21 per share, representing a premium of approximately 21% over Macy's closing price on Friday.

Notably, Pinterest (PINS) saw a 3% increase in its stock price after RBC Capital Markets upgraded the social media platform's rating to outperform from sector perform. Analyst Brad Erickson highlighted Pinterest's potential to capitalize on impulse spending in digital advertising. Additionally, the price target for Pinterest was raised to $46 from $32, emphasizing its strategic investment in intent-based ad platforms targeting impulse shopping.

On the other hand, BlackBerry (BB) faced a 5% decline in its shares following the appointment of John J. Giamatteo as the new CEO, replacing interim CEO Richard Lynch. Simultaneously, the company announced its plans to divide its Internet of Things and cybersecurity divisions into independent entities, scrapping the initial public offering for the IoT business. This restructuring aims to streamline corporate functions and foster financially sustainable operations for each segment.

In the cryptocurrency space, Bitcoin (BTC-USD) slipped 4%, marking its longest losing streak this month. The decline in Bitcoin affected the wider crypto market, with several companies experiencing downward pressure on their stock prices. Hive Digital Technologies (HIVE), Cipher Mining, and TeraWulf saw their shares decline by around 4%, while Bitfarms (BITF) dropped by 10%. CleanSpark (CLSK), Marathon Digital (MARA), and Hut 8 Mining (HUT) also faced declines of 8%, 6%, and 5% respectively. Additionally, Coinbase Global (COIN) and MicroStrategy (MSTR) saw their stocks fall by 4% and 3.5% respectively.

The stock market's movements on Monday showcased a mix of gains and losses for various entities. Cigna and Macy's emerged as winners amid strategic decisions and buyout offers, while BlackBerry and several cryptocurrency stocks faced downward pressure. Investors will continue to closely monitor these developments as the market unfolds.