The Stockholm Stock Exchange opened the shortened trading week in the red on Monday. On the domestic front, a new takeover bid was announced as private equity firm Altor seeks to acquire Sleep Cycle.

Abroad, Donald Trump's temperament flared up again on Sunday after receiving a response from Iran in the ongoing peace negotiations. Trump described the response as 'unacceptable', which has pushed Brent crude prices higher.

New macro data from China showed higher-than-expected exports in April. Inflation also rose more than anticipated during the same period.

At around 09:20, the OMXS30 index was down 0.30 percent at 3,064.54. Adjusted for dividends, the OMXS30 index was down 0.29 percent. Shares worth approximately SEK 1.5 billion were traded on the Stockholm Stock Exchange.

The best performing major industrial sector was energy, with an increase of 1.37 percent. At the other end of the scale, industrials lagged at the bottom, down 0.46 percent.

Among the leading shares included in the OMXS30 index, Ericsson B rose 1.2 percent while ABB was up 0.8 percent. The worst performers were Saab B, down 1.4 percent, and Sandvik, which fell 1.3 percent.

Sleep Cycle's shares woke up after private equity firm Altor, through the company Snark Bidco, launched a cash bid of SEK 24.5 per share. The offer represents a premium of 47 percent compared to Friday's closing price. The deal is valued at around SEK 497 million. Sleep Cycle surged 45 percent.

Among the morning's reports, figures from education company Academedia showed an increase in both revenue and operating profit during the third quarter of its broken fiscal year, compared to the same period last year. Adjusted operating profit rose to SEK 430 million from SEK 377 million. Academedia rose 2.8 percent.

Electrical technology company Garo is moving its production from Poland to Gnosjö and Hillerstorp in Sweden to streamline operations and strengthen competitiveness. The transition will be implemented gradually during the year and is expected to yield annual net savings of at least SEK 25 million. Garo also plans to sell its property in Poland, valued at between SEK 110 and 130 million. Furthermore, the sales office in Germany is being closed, which is expected to reduce costs by approximately SEK 5 million per year. Garo rose 5.6 percent.

Power and automation company ABB announced an investment of approximately USD 200 million to expand the manufacturing of medium-voltage equipment in Europe over three years. ABB climbed 0.8 percent.

Furthermore, aluminum profile company Profilgruppen has appointed Per Thorsell as the new CEO, effective May 18. Thorsell thus returns to the company after previously serving as CEO between 2014 and 2019. Profilgruppen rose 0.2 percent.

Research company Dicot Pharma has decided on a rights issue of units, approximately 80 percent guaranteed, of around SEK 210 million before issue costs. Dicot fell 3 percent.

In the analyst flow, Handelsbanken raised Balder to buy (hold), with a maintained target price of SEK 73. Balder retreated 4.5 percent.

Bank of America raises Verisure to buy (neutral). Verisure rose 2.1 percent.

SB1 Markets initiates coverage on Acast with a buy rating and a target price of SEK 45. Acast rose 0.9 percent.

SB1 Markets initiates coverage on Stillfront with a neutral rating and a target price of SEK 6. Stillfront rose 1 percent.

SB1 Markets initiates coverage on Engcon with a buy rating and a target price of SEK 90. Engcon rose 1.3 percent.

Dagens Industri issues a buy recommendation for Systemair. The stock rose 4.6 percent.